diff --git a/proselint/checks/social_awareness/__init__.py b/proselint/checks/social_awareness/__init__.py
index a69ec47ee..a173565c1 100644
--- a/proselint/checks/social_awareness/__init__.py
+++ b/proselint/checks/social_awareness/__init__.py
@@ -3,5 +3,6 @@
 from proselint.registry import build_modules_register
 
 __register__ = build_modules_register(
-    (".lgbtq", ".nword", ".sexism"), "proselint.checks.social_awareness"
+    (".lgbtq", ".nword", ".sexism", ".speciesism"),
+    "proselint.checks.social_awareness",
 )
diff --git a/proselint/checks/social_awareness/speciesism.py b/proselint/checks/social_awareness/speciesism.py
new file mode 100644
index 000000000..2314349b7
--- /dev/null
+++ b/proselint/checks/social_awareness/speciesism.py
@@ -0,0 +1,96 @@
+"""
+Speciesism.
+
+---
+layout:     post
+source:     Dunayer, J. (2001). Animal Equality: Language and Liberation.
+source_url: https://doi.org/10.1017/S0962728600024489
+title:      speciesism
+date:       2026-04-08 12:00:00
+categories: writing
+---
+
+Speciesism is the assumption of human superiority over other animals,
+expressed linguistically through idioms that treat animals as objects,
+nuisances, or inherently inferior beings. Joan Dunayer's *Animal Equality:
+Language and Liberation* (2001) is a foundational academic text examining
+how everyday language encodes and reinforces this bias.
+
+This check flags two categories of speciesist language:
+
+1. **Speciesist idioms** — common phrases whose imagery frames animals as
+   instruments (e.g. 'kill two birds with one stone'), pests (e.g. 'rat
+   race'), or property (e.g. 'cash cow'). Replacing these with neutral
+   alternatives improves clarity and avoids reinforcing the view that
+   animals exist primarily as means to human ends.
+
+2. **Animal comparisons used as insults** — similes that invoke animals to
+   describe human failings (e.g. 'eat like a pig', 'stubborn as a mule').
+   These expressions demean both the person and the animal, and clearer
+   alternatives are nearly always available.
+
+The idiom list uses Dunayer (2001) as its academic grounding. The specific
+phrases included draw on widely recognised speciesist language patterns in
+English usage; they are not all direct quotations or enumerated examples
+from that text.
+
+"""
+
+from proselint.registry.checks import Check, types
+
+CHECK_PATH = "social_awareness.speciesism"
+
+check_preferred_forms = Check(
+    check_type=types.PreferredFormsSimple(
+        items={
+            "kill two birds with one stone": "solve two problems at once",
+            "beat a dead horse": "belabor the point",
+            "wild goose chase": "futile search",
+            "let the cat out of the bag": "reveal the secret",
+            "guinea pig": "test subject",
+            "the elephant in the room": "the obvious issue",
+            "dog-eat-dog": "cutthroat",
+            "rat race": "daily grind",
+            "work like a dog": "work relentlessly",
+            "more than one way to skin a cat": "more than one way to solve this",
+            "open a can of worms": "create a new set of problems",
+            "hold your horses": "slow down",
+            "dark horse": "unexpected contender",
+            "straight from the horse's mouth": "from the original source",
+            "flog a dead horse": "belabor the point",
+            "take the bull by the horns": "tackle the problem directly",
+            "bull in a china shop": "clumsy or disruptive person",
+            "sacred cow": "untouchable assumption",
+            "cash cow": "reliable revenue source",
+            "herding cats": "managing an unruly group",
+            "let sleeping dogs lie": "avoid stirring up past trouble",
+            "barking up the wrong tree": "pursuing a mistaken course",
+            "cat got your tongue": "unable to speak",
+            "raining cats and dogs": "raining heavily",
+            "bird's-eye view": "aerial view",
+            "cold turkey": "abruptly",
+        }
+    ),
+    path=CHECK_PATH,
+    message="Speciesist idiom. Consider '{}' instead of '{}'.",
+)
+
+check_derogatory = Check(
+    check_type=types.PreferredFormsSimple(
+        items={
+            "eat like a pig": "eat ravenously",
+            "stubborn as a mule": "extremely stubborn",
+            "blind as a bat": "completely blind",
+            "quiet as a mouse": "extremely quiet",
+            "drunk as a skunk": "extremely drunk",
+            "fat as a pig": "overweight",
+            "sweating like a pig": "sweating heavily",
+            "slow as a snail": "extremely slow",
+            "memory like a goldfish": "short memory",
+        }
+    ),
+    path=CHECK_PATH,
+    message="Animal comparison used as an insult. Consider '{}' instead of '{}'.",
+)
+
+__register__ = (check_preferred_forms, check_derogatory)
diff --git a/tests/examples.py b/tests/examples.py
index f69013a90..34aea7786 100644
--- a/tests/examples.py
+++ b/tests/examples.py
@@ -612,6 +612,23 @@
             "Hello Mr. birdperson. still looking good.",
         ),
     ),
+    (
+        "social_awareness.speciesism",
+        (
+            "We need to kill two birds with one stone here.",
+            "Stop beating a dead horse.",
+            "He used a guinea pig for his experiment.",
+            "There's an elephant in the room.",
+            "She eats like a pig.",
+            "He's as stubborn as a mule.",
+        ),
+        (
+            "Smoke phrase with nothing flagged.",
+            "We need to solve two problems at once.",
+            "Stop belaboring the point.",
+            "He used a test subject for his experiment.",
+        ),
+    ),
     (
         "spelling.consistency",
         (