diff --git a/Funcky.Test/Extensions/ImmutableListExtensions/IndexOfOrNoneTest.cs b/Funcky.Test/Extensions/ImmutableListExtensions/IndexOfOrNoneTest.cs
index 28bc09d7..f9575a41 100644
--- a/Funcky.Test/Extensions/ImmutableListExtensions/IndexOfOrNoneTest.cs
+++ b/Funcky.Test/Extensions/ImmutableListExtensions/IndexOfOrNoneTest.cs
@@ -55,4 +55,11 @@ public void GivenZeroIndexIndexOfOrNoneReturnsNone()
         FunctionalAssert.None(list.IndexOfOrNone("Gamma", 0));
         FunctionalAssert.None(list.IndexOfOrNone("Gamma", 0, 0));
     }
+
+    [Fact]
+    public void CallIsNotAmbiguousWhenUsedOnConcreteTypes()
+    {
+        _ = ImmutableArray<string>.Empty.IndexOfOrNone("foo");
+        _ = ImmutableList<string>.Empty.IndexOfOrNone("foo");
+    }
 }
diff --git a/Funcky/Extensions/ImmutableListExtensions/IndexOfOrNone.cs b/Funcky/Extensions/ListExtensions/IImmutableList.IndexOfOrNone.cs
similarity index 98%
rename from Funcky/Extensions/ImmutableListExtensions/IndexOfOrNone.cs
rename to Funcky/Extensions/ListExtensions/IImmutableList.IndexOfOrNone.cs
index d8194360..d3b326f0 100644
--- a/Funcky/Extensions/ImmutableListExtensions/IndexOfOrNone.cs
+++ b/Funcky/Extensions/ListExtensions/IImmutableList.IndexOfOrNone.cs
@@ -1,9 +1,10 @@
 using System.Collections.Immutable;
+using System.Runtime.CompilerServices;
 using static Funcky.Internal.ValueMapper;
 
 namespace Funcky.Extensions;
 
-public static partial class ImmutableListExtensions
+public static partial class ListExtensions
 {
     /// <summary>
     /// Searches for the specified object and returns the zero-based index of the first occurrence within the range of elements in the <see cref="IImmutableList{T}" /> that starts at the specified index and contains the specified number of elements.
@@ -25,6 +26,7 @@ public static Option<int> IndexOfOrNone<TItem>(this IImmutableList<TItem> list,
     /// <param name="list">An <see cref="IImmutableList{T}" /> of values.</param>
     /// <param name="item">The object to locate in the <see cref="T:System.Collections.Immutable.IImmutableList`1" />. This value can be null for reference types.</param>
     /// <returns>The zero-based index of the first occurrence of <paramref name="item" /> within the range of elements in the <see cref="IImmutableList{T}" /> if found; otherwise <see cref="Option{T}.None" />.</returns>
+    [OverloadResolutionPriority(1)]
     public static Option<int> IndexOfOrNone<TItem>(this IImmutableList<TItem> list, TItem item)
         => MapNotFoundToNone(list.IndexOf(item));
 
diff --git a/Funcky/Extensions/ImmutableListExtensions/LastIndexOfOrNone.cs b/Funcky/Extensions/ListExtensions/IImmutableList.LastIndexOfOrNone.cs
similarity index 99%
rename from Funcky/Extensions/ImmutableListExtensions/LastIndexOfOrNone.cs
rename to Funcky/Extensions/ListExtensions/IImmutableList.LastIndexOfOrNone.cs
index 044b31f8..b4c4c9d3 100644
--- a/Funcky/Extensions/ImmutableListExtensions/LastIndexOfOrNone.cs
+++ b/Funcky/Extensions/ListExtensions/IImmutableList.LastIndexOfOrNone.cs
@@ -3,7 +3,7 @@
 
 namespace Funcky.Extensions;
 
-public static partial class ImmutableListExtensions
+public static partial class ListExtensions
 {
     /// <summary>
     /// Searches for the specified object and returns the zero-based index of the last occurrence within the range of elements in the <see cref="IImmutableList{T}" /> that contains the specified number of elements and ends at the specified index.
diff --git a/Funcky/Extensions/ListExtensions/IList.cs b/Funcky/Extensions/ListExtensions/IList.cs
new file mode 100644
index 00000000..90cafe42
--- /dev/null
+++ b/Funcky/Extensions/ListExtensions/IList.cs
@@ -0,0 +1,10 @@
+using static Funcky.Internal.ValueMapper;
+
+namespace Funcky.Extensions;
+
+public static partial class ListExtensions
+{
+    [Pure]
+    public static Option<int> IndexOfOrNone<TValue>(this IList<TValue> list, TValue value)
+        => MapNotFoundToNone(list.IndexOf(value));
+}
diff --git a/Funcky/Extensions/ListExtensions.cs b/Funcky/Extensions/ListExtensions/List.cs
similarity index 86%
rename from Funcky/Extensions/ListExtensions.cs
rename to Funcky/Extensions/ListExtensions/List.cs
index 01a67ef5..ed80b0bd 100644
--- a/Funcky/Extensions/ListExtensions.cs
+++ b/Funcky/Extensions/ListExtensions/List.cs
@@ -2,12 +2,8 @@
 
 namespace Funcky.Extensions;
 
-public static class ListExtensions
+public static partial class ListExtensions
 {
-    [Pure]
-    public static Option<int> IndexOfOrNone<TValue>(this IList<TValue> list, TValue value)
-        => MapNotFoundToNone(list.IndexOf(value));
-
     [Pure]
     public static Option<int> FindIndexOrNone<TValue>(this List<TValue> list, Predicate<TValue> match)
         => MapNotFoundToNone(list.FindIndex(match));
diff --git a/Funcky/Obsolete/ImmutableListExtensions/IndexOfOrNone.cs b/Funcky/Obsolete/ImmutableListExtensions/IndexOfOrNone.cs
new file mode 100644
index 00000000..ac4cf56a
--- /dev/null
+++ b/Funcky/Obsolete/ImmutableListExtensions/IndexOfOrNone.cs
@@ -0,0 +1,60 @@
+using System.Collections.Immutable;
+using System.ComponentModel;
+using static Funcky.Internal.ValueMapper;
+
+namespace Funcky.Extensions;
+
+[EditorBrowsable(EditorBrowsableState.Never)]
+[Obsolete($"Use {nameof(ListExtensions)} instead.")]
+public static partial class ImmutableListExtensions
+{
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(IndexOfOrNone)} instead.")]
+    public static Option<int> IndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item, int startIndex, int count, IEqualityComparer<TItem>? equalityComparer)
+        => MapNotFoundToNone(list.IndexOf(item, startIndex, count, equalityComparer));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(IndexOfOrNone)} instead.")]
+    public static Option<int> IndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item)
+        => MapNotFoundToNone(list.IndexOf(item));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(IndexOfOrNone)} instead.")]
+    public static Option<int> IndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item, IEqualityComparer<TItem>? equalityComparer)
+        => MapNotFoundToNone(list.IndexOf(item, equalityComparer));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(IndexOfOrNone)} instead.")]
+    public static Option<int> IndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item, int startIndex)
+        => MapNotFoundToNone(list.IndexOf(item, startIndex));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(IndexOfOrNone)} instead.")]
+    public static Option<int> IndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item, int startIndex, int count)
+        => MapNotFoundToNone(list.IndexOf(item, startIndex, count));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(LastIndexOfOrNone)} instead.")]
+    public static Option<int> LastIndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item, int startIndex, int count, IEqualityComparer<TItem>? equalityComparer)
+        => MapNotFoundToNone(list.LastIndexOf(item, startIndex, count, equalityComparer));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(LastIndexOfOrNone)} instead.")]
+    public static Option<int> LastIndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item)
+        => MapNotFoundToNone(list.LastIndexOf(item));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(LastIndexOfOrNone)} instead.")]
+    public static Option<int> LastIndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item, IEqualityComparer<TItem>? equalityComparer)
+        => MapNotFoundToNone(list.LastIndexOf(item, equalityComparer));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(LastIndexOfOrNone)} instead.")]
+    public static Option<int> LastIndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item, int startIndex)
+        => MapNotFoundToNone(list.LastIndexOf(item, startIndex));
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete($"Use {nameof(ListExtensions)}.{nameof(LastIndexOfOrNone)} instead.")]
+    public static Option<int> LastIndexOfOrNone<TItem>(IImmutableList<TItem> list, TItem item, int startIndex, int count)
+        => MapNotFoundToNone(list.LastIndexOf(item, startIndex, count));
+}
diff --git a/Funcky/PublicAPI.Shipped.txt b/Funcky/PublicAPI.Shipped.txt
index 6200312d..2650399f 100644
--- a/Funcky/PublicAPI.Shipped.txt
+++ b/Funcky/PublicAPI.Shipped.txt
@@ -363,16 +363,16 @@ static Funcky.Extensions.FuncExtensions.Uncurry<T1, T2, T3, TResult>(this System
 static Funcky.Extensions.FuncExtensions.Uncurry<T1, T2, TResult>(this System.Func<T1, System.Func<T2, TResult>!>! function) -> System.Func<T1, T2, TResult>!
 static Funcky.Extensions.HttpHeadersExtensions.GetValuesOrNone(this System.Net.Http.Headers.HttpHeaders! headers, string! name) -> Funcky.Monads.Option<System.Collections.Generic.IEnumerable<string!>!>
 static Funcky.Extensions.HttpHeadersNonValidatedExtensions.GetValuesOrNone(this System.Net.Http.Headers.HttpHeadersNonValidated headers, string! headerName) -> Funcky.Monads.Option<System.Net.Http.Headers.HeaderStringValues>
-static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
-static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.IndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ImmutableListExtensions.LastIndexOfOrNone<TItem>(System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
 static Funcky.Extensions.ListExtensions.FindIndexOrNone<TValue>(this System.Collections.Generic.List<TValue>! list, int startIndex, int count, System.Predicate<TValue>! match) -> Funcky.Monads.Option<int>
 static Funcky.Extensions.ListExtensions.FindIndexOrNone<TValue>(this System.Collections.Generic.List<TValue>! list, int startIndex, System.Predicate<TValue>! match) -> Funcky.Monads.Option<int>
 static Funcky.Extensions.ListExtensions.FindIndexOrNone<TValue>(this System.Collections.Generic.List<TValue>! list, System.Predicate<TValue>! match) -> Funcky.Monads.Option<int>
diff --git a/Funcky/PublicAPI.Unshipped.txt b/Funcky/PublicAPI.Unshipped.txt
index b3855253..151a8982 100644
--- a/Funcky/PublicAPI.Unshipped.txt
+++ b/Funcky/PublicAPI.Unshipped.txt
@@ -58,6 +58,16 @@ static Funcky.Extensions.FuncExtensions.Apply<T1, T2, T3, TResult>(this System.F
 static Funcky.Extensions.FuncExtensions.Apply<T1, T2, TResult>(this System.Func<T1, T2, TResult>! func, Funcky.Unit p1, T2 p2) -> System.Func<T1, TResult>!
 static Funcky.Extensions.FuncExtensions.Apply<T1, T2, TResult>(this System.Func<T1, T2, TResult>! func, T1 p1, Funcky.Unit p2) -> System.Func<T2, TResult>!
 static Funcky.Extensions.JsonSerializerOptionsExtensions.GetTypeInfoOrNone(this System.Text.Json.JsonSerializerOptions! options, System.Type! type) -> Funcky.Monads.Option<System.Text.Json.Serialization.Metadata.JsonTypeInfo!>
+static Funcky.Extensions.ListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.IndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, int startIndex, int count, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
+static Funcky.Extensions.ListExtensions.LastIndexOfOrNone<TItem>(this System.Collections.Immutable.IImmutableList<TItem>! list, TItem item, System.Collections.Generic.IEqualityComparer<TItem>? equalityComparer) -> Funcky.Monads.Option<int>
 static Funcky.Extensions.OrderedDictionaryExtensions.IndexOfOrNone<TKey, TValue>(this System.Collections.Generic.OrderedDictionary<TKey, TValue>! dictionary, TKey key) -> Funcky.Monads.Option<int>
 static Funcky.Extensions.ParseExtensions.ParseIPNetworkOrNone(this string? candidate) -> Funcky.Monads.Option<System.Net.IPNetwork>
 static Funcky.Extensions.ParseExtensions.ParseIPNetworkOrNone(this System.ReadOnlySpan<char> candidate) -> Funcky.Monads.Option<System.Net.IPNetwork>