diff --git a/coremltools/converters/mil/frontend/torch/ops.py b/coremltools/converters/mil/frontend/torch/ops.py
index d2470423c..3e8a6694d 100644
--- a/coremltools/converters/mil/frontend/torch/ops.py
+++ b/coremltools/converters/mil/frontend/torch/ops.py
@@ -5796,7 +5796,11 @@ def bitwise_and(context, node):
 # which torch.export emits for `tensor | tensor` / `tensor ^ tensor`. These are
 # common when building boolean attention masks (e.g. Gemma combines a causal
 # mask with a padding mask via __or__).
-@register_torch_op(torch_alias=["or"])
+#
+# "ior" is the post-sanitize form of "aten::__ior__", the in-place `|=`.
+# `sanitize_op_kind` only strips a trailing `_`, so the leading `i` in the
+# `__i<op>__` family is preserved -- the alias has to be listed explicitly.
+@register_torch_op(torch_alias=["or", "ior"])
 def bitwise_or(context, node):
     _bitwise_as_logical_if_boolean(context, node, "bitwise_or", logical_or)
 
diff --git a/coremltools/converters/mil/frontend/torch/test/test_torch_ops.py b/coremltools/converters/mil/frontend/torch/test/test_torch_ops.py
index 00dd7f5f9..4b7bb38c8 100644
--- a/coremltools/converters/mil/frontend/torch/test/test_torch_ops.py
+++ b/coremltools/converters/mil/frontend/torch/test/test_torch_ops.py
@@ -13754,6 +13754,41 @@ def forward(self, x, y):
             input_as_shape=False,
         )
 
+    @pytest.mark.parametrize(
+        "compute_unit, backend",
+        itertools.product(compute_units, backends),
+    )
+    def test_ior_operator(self, compute_unit, backend):
+        # Regression test for issue #2584: TorchScript trace of `z |= y`
+        # records `aten::__ior__`, which sanitizes to "ior" and must be
+        # registered as an alias of bitwise_or. Previously gemma-3-1b-it
+        # conversion failed with
+        # "PyTorch convert function for op '__ior__' not implemented."
+        #
+        # Notes on scope:
+        # * Core ML inputs are immutable, so the model clones an input
+        #   before mutating it; without the clone, `run_compare_torch`
+        #   would raise the unrelated user-input-mutation guard.
+        # * torch.export decomposes `__ior__` into `clone + bitwise_or`,
+        #   so the new alias is only reachable via the TorchScript path.
+        class TestModel(torch.nn.Module):
+            def forward(self, x, y):
+                z = x.clone()
+                z |= y
+                return z
+
+        input_shape = (2, 3)
+        input_data_x = torch.rand(*input_shape) > 0.2
+        input_data_y = torch.rand(*input_shape) < 0.8
+        self.run_compare_torch(
+            [input_data_x, input_data_y],
+            TestModel(),
+            frontend=TorchFrontend.TORCHSCRIPT,
+            backend=backend,
+            compute_unit=compute_unit,
+            input_as_shape=False,
+        )
+
 
 class TestBitwiseXor(TorchBaseTest):
     @pytest.mark.parametrize(