diff --git a/README.md b/README.md
index f853ae1..b684a56 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,12 @@ aliasor.partial_compress("B.1.1.529.3.1",accepted_aliases=["AY"]) # 'B.1.1.529.3
 aliasor.partial_compress("B.1.617.2",accepted_aliases=["AY"]) # 'AY.2'
 
 aliasor.partial_compress('B.1.1.529.2.75.1.2',up_to=4, accepted_aliases={"BA"}) == 'BL.2'
+
+# Compress an uncompressed_lineage up to the first potential_parent lineage. If no parents are found return the uncompressed_lineage.
+aliasor.collapse("B.1.1.529.3.1", potential_parents=['BA.3']) # 'BA.3'
+aliasor.collapse("B.1.1.529.3.1", potential_parents=['BA.3', 'BA.3.1']) # 'BA.3.1'
+aliasor.collapse("B.1.1.529.3.1", potential_parents=['B.1.1', 'BZ.1', 'AY.4']) # 'B.1.1'
+aliasor.collapse("B.1.1.529.3.1", potential_parents=['A']) # "B.1.1.529.3.1"
 ```
 
 See [tests](tests/test_aliasor.py) for more examples.
diff --git a/src/pango_aliasor/aliasor.py b/src/pango_aliasor/aliasor.py
index 92eff1e..a92afb8 100644
--- a/src/pango_aliasor/aliasor.py
+++ b/src/pango_aliasor/aliasor.py
@@ -1,4 +1,7 @@
 #%%
+from typing import List
+
+
 class Aliasor:
     def __init__(self, alias_file=None):
         import json
@@ -82,5 +85,28 @@ def partial_compress(self, name, up_to: int = 0, accepted_aliases: set = {}):
 
         return alias + "." + ".".join(name_split[(3 * up_to + 1) :])
 
+    def collapse(self, uncompressed_lineage: str, potential_parents: List[str]):
+        """
+        Compress an uncompressed_lineage up to the first potential_parent lineage.
+        If no parents are found return the uncompressed_lineage.
+        
+        aliasor.collapse("B.1.1.529.3.1", potential_parents=['BA.3']) # 'BA.3'
+
+        aliasor.collapse("B.1.1.529.3.1", potential_parents=['BA.3', 'BA.3.1']) # 'BA.3.1'
+
+        aliasor.collapse("B.1.1.529.3.1", potential_parents=['B.1.1', 'BZ.1', 'AY.4']) # 'B.1.1'
+
+        aliasor.collapse("B.1.1.529.3.1", potential_parents=['A']) # "B.1.1.529.3.1"
+        """
+        compressed_lineage = self.compress(uncompressed_lineage)
+        if compressed_lineage in potential_parents:
+            return compressed_lineage
+        parts = uncompressed_lineage.split(".")
+        compressed_parent_lineage = uncompressed_lineage
+        for i in range(1, len(parts)):
+            compressed_parent_lineage = self.compress(".".join(parts[:-i]))
+            if compressed_parent_lineage in potential_parents:
+                return compressed_parent_lineage
+        return uncompressed_lineage
 
 # %%
diff --git a/tests/test_aliasor.py b/tests/test_aliasor.py
index 67da938..bef05ea 100644
--- a/tests/test_aliasor.py
+++ b/tests/test_aliasor.py
@@ -79,4 +79,12 @@ def test_partial_alias_combination():
     assert aliasor.partial_compress('B.1.617.2.3',up_to=1, accepted_aliases={"BA","AZ"}) == "AY.3"
     assert aliasor.partial_compress('B.1.1.529.2.75.1.2',up_to=3, accepted_aliases={"BA"}) == 'BL.2'
     assert aliasor.partial_compress('B.1.1.529.2.75.1.2',up_to=4, accepted_aliases={"BA"}) == 'BL.2'
-    assert aliasor.partial_compress('B.1.1.529.2.75.1.2',up_to=1, accepted_aliases={"BA"}) == 'BA.2.75.1.2'
\ No newline at end of file
+    assert aliasor.partial_compress('B.1.1.529.2.75.1.2',up_to=1, accepted_aliases={"BA"}) == 'BA.2.75.1.2'
+
+def test_collapse():
+    aliasor = Aliasor()
+    assert aliasor.collapse('B.1.1.529.3.1', potential_parents=['BA.3']) == 'BA.3'
+    assert aliasor.collapse('B.1.1.529.3.1', potential_parents=['BA.3', 'BA.3.1']) == 'BA.3.1'
+    assert aliasor.collapse('B.1.1.529.3.1', potential_parents=['B.1.1', 'BZ.1', 'AY.4']) == 'B.1.1'
+    assert aliasor.collapse('B.1.1.529.3.1', potential_parents=['A']) == 'B.1.1.529.3.1'
+    assert aliasor.collapse('XA.1', potential_parents=['B.1.1', 'BZ.1', 'AY.4']) == 'XA.1'
\ No newline at end of file