diff --git a/src/poetry/core/version/markers.py b/src/poetry/core/version/markers.py
index 57715f259..6ce2ccb42 100644
--- a/src/poetry/core/version/markers.py
+++ b/src/poetry/core/version/markers.py
@@ -501,6 +501,9 @@ def union_simplify(self, other: BaseMarker) -> BaseMarker | None:
             ):
                 return other
 
+            if not any(isinstance(m, MarkerUnion) for m in new_markers):
+                return self.of(*new_markers)
+
         elif isinstance(other, MultiMarker):
             common_markers = [
                 marker for marker in self.markers if marker in other.markers
@@ -525,6 +528,23 @@ def union_simplify(self, other: BaseMarker) -> BaseMarker | None:
                 if not isinstance(unique_union, MarkerUnion):
                     return self.of(*common_markers).intersect(unique_union)
 
+            else:
+                # Usually this operation just complicates things, but the special case
+                # where it doesn't allows the collapse of adjacent ranges eg
+                #
+                # 'python_version >= "3.6" and python_version < "3.6.2"' union
+                # 'python_version >= "3.6.2" and python_version < "3.7"' ->
+                #
+                # 'python_version >= "3.6" and python_version < "3.7"'.
+                unions = [
+                    m1.union(m2) for m2 in other_unique_markers for m1 in unique_markers
+                ]
+                conjunction = self.of(*unions)
+                if not isinstance(conjunction, MultiMarker) or not any(
+                    isinstance(m, MarkerUnion) for m in conjunction.markers
+                ):
+                    return conjunction
+
         return None
 
     def validate(self, environment: dict[str, Any] | None) -> bool:
diff --git a/tests/version/test_markers.py b/tests/version/test_markers.py
index 65dc70516..9bf900c47 100644
--- a/tests/version/test_markers.py
+++ b/tests/version/test_markers.py
@@ -481,6 +481,90 @@ def test_multi_marker_union_multi_is_multi(
     assert str(m2.union(m1)) == expected
 
 
+@pytest.mark.parametrize(
+    "marker1, marker2, expected",
+    [
+        # Ranges with same start
+        (
+            'python_version >= "3.6" and python_full_version < "3.6.2"',
+            'python_version >= "3.6" and python_version < "3.7"',
+            'python_version >= "3.6" and python_version < "3.7"',
+        ),
+        (
+            'python_version > "3.6" and python_full_version < "3.6.2"',
+            'python_version > "3.6" and python_version < "3.7"',
+            'python_version > "3.6" and python_version < "3.7"',
+        ),
+        # Ranges meet exactly
+        (
+            'python_version >= "3.6" and python_full_version < "3.6.2"',
+            'python_full_version >= "3.6.2" and python_version < "3.7"',
+            'python_version >= "3.6" and python_version < "3.7"',
+        ),
+        (
+            'python_version >= "3.6" and python_full_version <= "3.6.2"',
+            'python_full_version > "3.6.2" and python_version < "3.7"',
+            'python_version >= "3.6" and python_version < "3.7"',
+        ),
+        # Ranges overlap
+        (
+            'python_version >= "3.6" and python_full_version <= "3.6.8"',
+            'python_full_version >= "3.6.2" and python_version < "3.7"',
+            'python_version >= "3.6" and python_version < "3.7"',
+        ),
+        # Ranges with same end.  Ideally the union would give the lower version first.
+        (
+            'python_version >= "3.6" and python_version < "3.7"',
+            'python_full_version >= "3.6.2" and python_version < "3.7"',
+            'python_version < "3.7" and python_version >= "3.6"',
+        ),
+        (
+            'python_version >= "3.6" and python_version <= "3.7"',
+            'python_full_version >= "3.6.2" and python_version <= "3.7"',
+            'python_version <= "3.7" and python_version >= "3.6"',
+        ),
+        # A range covers an exact marker.
+        (
+            'python_version >= "3.6" and python_version <= "3.7"',
+            'python_version == "3.6"',
+            'python_version >= "3.6" and python_version <= "3.7"',
+        ),
+        (
+            'python_version >= "3.6" and python_version <= "3.7"',
+            'python_version == "3.6" and implementation_name == "cpython"',
+            'python_version >= "3.6" and python_version <= "3.7"',
+        ),
+        (
+            'python_version >= "3.6" and python_version <= "3.7"',
+            'python_full_version == "3.6.2"',
+            'python_version >= "3.6" and python_version <= "3.7"',
+        ),
+        (
+            'python_version >= "3.6" and python_version <= "3.7"',
+            'python_full_version == "3.6.2" and implementation_name == "cpython"',
+            'python_version >= "3.6" and python_version <= "3.7"',
+        ),
+        (
+            'python_version >= "3.6" and python_version <= "3.7"',
+            'python_version == "3.7"',
+            'python_version >= "3.6" and python_version <= "3.7"',
+        ),
+        (
+            'python_version >= "3.6" and python_version <= "3.7"',
+            'python_version == "3.7" and implementation_name == "cpython"',
+            'python_version >= "3.6" and python_version <= "3.7"',
+        ),
+    ],
+)
+def test_version_ranges_collapse_on_union(
+    marker1: str, marker2: str, expected: str
+) -> None:
+    m1 = parse_marker(marker1)
+    m2 = parse_marker(marker2)
+    assert str(m1.union(m2)) == expected
+    assert str(m2.union(m1)) == expected
+
+
 def test_multi_marker_union_with_union() -> None:
     m = parse_marker('sys_platform == "darwin" and implementation_name == "cpython"')
 
@@ -964,8 +1048,8 @@ def test_union_of_multi_with_a_containing_single() -> None:
             'python_version < "3.6" or python_version >= "4.0"',
         ),
         (
-            'python_version ~= "3.6.3"',
-            'python_version < "3.6.3" or python_version >= "3.7.0"',
+            'python_full_version ~= "3.6.3"',
+            'python_full_version < "3.6.3" or python_full_version >= "3.7.0"',
         ),
     ],
 )