diff --git a/libc/utils/hdrgen/enumeration.py b/libc/utils/hdrgen/enumeration.py
index b9848c04ee632..198720826720c 100644
--- a/libc/utils/hdrgen/enumeration.py
+++ b/libc/utils/hdrgen/enumeration.py
@@ -6,12 +6,24 @@
 #
 # ==-------------------------------------------------------------------------==#
 
+from functools import total_ordering
 
+
+@total_ordering
 class Enumeration:
     def __init__(self, name, value):
         self.name = name
         self.value = value
 
+    def __eq__(self, other):
+        return self.name == other.name
+
+    def __lt__(self, other):
+        return self.name < other.name
+
+    def __hash__(self):
+        return self.name.__hash__()
+
     def __str__(self):
         if self.value != None:
             return f"{self.name} = {self.value}"
diff --git a/libc/utils/hdrgen/function.py b/libc/utils/hdrgen/function.py
index 25a7fa80e4501..bccd2c2caa2f5 100644
--- a/libc/utils/hdrgen/function.py
+++ b/libc/utils/hdrgen/function.py
@@ -7,6 +7,7 @@
 # ==-------------------------------------------------------------------------==#
 
 import re
+from functools import total_ordering
 from type import Type
 
 
@@ -36,6 +37,7 @@
 NONIDENTIFIER = re.compile("[^a-zA-Z0-9_]+")
 
 
+@total_ordering
 class Function:
     def __init__(
         self, return_type, name, arguments, standards, guard=None, attributes=[]
@@ -51,6 +53,15 @@ def __init__(
         self.guard = guard
         self.attributes = attributes or []
 
+    def __eq__(self, other):
+        return self.name == other.name
+
+    def __lt__(self, other):
+        return self.name < other.name
+
+    def __hash__(self):
+        return self.name.__hash__()
+
     def signature_types(self):
         def collapse(type_string):
             assert type_string
diff --git a/libc/utils/hdrgen/header.py b/libc/utils/hdrgen/header.py
index 685e5730e681e..9ea9f98f8fc83 100644
--- a/libc/utils/hdrgen/header.py
+++ b/libc/utils/hdrgen/header.py
@@ -73,6 +73,7 @@ def __init__(self, name):
         self.objects = []
         self.functions = []
         self.standards = []
+        self.merge_yaml_files = []
 
     def add_macro(self, macro):
         self.macros.append(macro)
@@ -89,6 +90,13 @@ def add_object(self, object):
     def add_function(self, function):
         self.functions.append(function)
 
+    def merge(self, other):
+        self.macros = sorted(set(self.macros) | set(other.macros))
+        self.types = sorted(set(self.types) | set(other.types))
+        self.enumerations = sorted(set(self.enumerations) | set(other.enumerations))
+        self.objects = sorted(set(self.objects) | set(other.objects))
+        self.functions = sorted(set(self.functions) | set(other.functions))
+
     def all_types(self):
         return reduce(
             lambda a, b: a | b,
diff --git a/libc/utils/hdrgen/macro.py b/libc/utils/hdrgen/macro.py
index 19c2b318b8f77..e42e82845694d 100644
--- a/libc/utils/hdrgen/macro.py
+++ b/libc/utils/hdrgen/macro.py
@@ -6,13 +6,25 @@
 #
 # ==-------------------------------------------------------------------------==#
 
+from functools import total_ordering
 
+
+@total_ordering
 class Macro:
     def __init__(self, name, value=None, header=None):
         self.name = name
         self.value = value
         self.header = header
 
+    def __eq__(self, other):
+        return self.name == other.name
+
+    def __lt__(self, other):
+        return self.name < other.name
+
+    def __hash__(self):
+        return self.name.__hash__()
+
     def __str__(self):
         if self.header != None:
             return ""
diff --git a/libc/utils/hdrgen/main.py b/libc/utils/hdrgen/main.py
index af57845582e5e..27b21ce8ca44b 100755
--- a/libc/utils/hdrgen/main.py
+++ b/libc/utils/hdrgen/main.py
@@ -52,8 +52,7 @@ def main():
     )
     args = parser.parse_args()
 
-    [yaml_file] = args.yaml_file
-    files_read = {yaml_file}
+    files_read = set()
 
     def write_depfile():
         if not args.depfile:
@@ -63,7 +62,34 @@ def write_depfile():
         with open(args.depfile, "w") as depfile:
             depfile.write(f"{args.output}: {deps}\n")
 
-    header = load_yaml_file(yaml_file, HeaderFile, args.entry_point)
+    def load_yaml(path):
+        files_read.add(path)
+        return load_yaml_file(path, HeaderFile, args.entry_point)
+
+    merge_from_files = dict()
+
+    def merge_from(paths):
+        for path in paths:
+            # Load each file exactly once, in case of redundant merges.
+            if path in merge_from_files:
+                continue
+            header = load_yaml(path)
+            merge_from_files[path] = header
+            merge_from(path.parent / f for f in header.merge_yaml_files)
+
+    # Load the main file first.
+    [yaml_file] = args.yaml_file
+    header = load_yaml(yaml_file)
+
+    # Now load all the merge_yaml_files, and any transitive merge_yaml_files.
+    merge_from(yaml_file.parent / f for f in header.merge_yaml_files)
+
+    # Merge in all those files' contents.
+    for merge_from_path, merge_from_header in merge_from_files.items():
+        if merge_from_header.name is not None:
+            print(f"{merge_from_path!s}: Merge file cannot have header field", stderr)
+            return 2
+        header.merge(merge_from_header)
 
     # The header_template path is relative to the containing YAML file.
     template = header.template(yaml_file.parent, files_read)
diff --git a/libc/utils/hdrgen/object.py b/libc/utils/hdrgen/object.py
index f5214452f0349..a311c37168d60 100644
--- a/libc/utils/hdrgen/object.py
+++ b/libc/utils/hdrgen/object.py
@@ -6,11 +6,23 @@
 #
 # ==-------------------------------------------------------------------------==#
 
+from functools import total_ordering
 
+
+@total_ordering
 class Object:
     def __init__(self, name, type):
         self.name = name
         self.type = type
 
+    def __eq__(self, other):
+        return self.name == other.name
+
+    def __lt__(self, other):
+        return self.name < other.name
+
+    def __hash__(self):
+        return self.name.__hash__()
+
     def __str__(self):
         return f"extern {self.type} {self.name};"
diff --git a/libc/utils/hdrgen/tests/input/merge1.yaml b/libc/utils/hdrgen/tests/input/merge1.yaml
new file mode 100644
index 0000000000000..950abd1770320
--- /dev/null
+++ b/libc/utils/hdrgen/tests/input/merge1.yaml
@@ -0,0 +1,19 @@
+macros:
+  - macro_name: MACRO_A
+    macro_value: 1
+types:
+  - type_name: type_a
+enums:
+  - name: enum_a
+    value: value_1
+objects:
+  - object_name: object_1
+    object_type: obj
+functions:
+  - name: func_a
+    return_type: void
+    arguments: []
+    standards:
+      - stdc
+    attributes:
+      - CONST_FUNC_A
diff --git a/libc/utils/hdrgen/tests/input/merge2.yaml b/libc/utils/hdrgen/tests/input/merge2.yaml
new file mode 100644
index 0000000000000..a5d741454c3d7
--- /dev/null
+++ b/libc/utils/hdrgen/tests/input/merge2.yaml
@@ -0,0 +1,18 @@
+macros:
+  - macro_name: MACRO_B
+    macro_value: 2
+types:
+  - type_name: type_b
+enums:
+  - name: enum_b
+    value: value_2
+objects:
+  - object_name: object_2
+    object_type: obj
+functions:
+  - name: func_b
+    return_type: float128
+    arguments: []
+    standards:
+      - stdc
+    guard: LIBC_TYPES_HAS_FLOAT128
diff --git a/libc/utils/hdrgen/tests/input/test_small.yaml b/libc/utils/hdrgen/tests/input/test_small.yaml
index d5bb2bbfe4468..e072239e9a02a 100644
--- a/libc/utils/hdrgen/tests/input/test_small.yaml
+++ b/libc/utils/hdrgen/tests/input/test_small.yaml
@@ -1,42 +1,15 @@
 header: test_small.h
 header_template: test_small.h.def
+merge_yaml_files:
+  - merge1.yaml
+  - merge2.yaml
 macros:
-  - macro_name: MACRO_A
-    macro_value: 1
-  - macro_name: MACRO_B
-    macro_value: 2
   - macro_name: MACRO_C
   - macro_name: MACRO_D
     macro_header: test_small-macros.h
   - macro_name: MACRO_E
     macro_header: test_more-macros.h
-types:
-  - type_name: type_a
-  - type_name: type_b
-enums:
-  - name: enum_a
-    value: value_1
-  - name: enum_b
-    value: value_2
-objects:
-  - object_name: object_1
-    object_type: obj
-  - object_name: object_2
-    object_type: obj
 functions:
-  - name: func_a
-    return_type: void
-    arguments: []
-    standards:
-      - stdc
-    attributes:
-      - CONST_FUNC_A
-  - name: func_b
-    return_type: float128
-    arguments: []
-    standards:
-      - stdc
-    guard: LIBC_TYPES_HAS_FLOAT128
   - name: func_c
     return_type: _Float16
     arguments:
diff --git a/libc/utils/hdrgen/type.py b/libc/utils/hdrgen/type.py
index 0dbd8a5837d15..0c0af8569c61e 100644
--- a/libc/utils/hdrgen/type.py
+++ b/libc/utils/hdrgen/type.py
@@ -6,7 +6,10 @@
 #
 # ==-------------------------------------------------------------------------==#
 
+from functools import total_ordering
 
+
+@total_ordering
 class Type:
     def __init__(self, type_name):
         assert type_name
@@ -15,5 +18,8 @@ def __init__(self, type_name):
     def __eq__(self, other):
         return self.type_name == other.type_name
 
+    def __lt__(self, other):
+        return self.type_name < other.type_name
+
     def __hash__(self):
         return self.type_name.__hash__()
diff --git a/libc/utils/hdrgen/yaml_to_classes.py b/libc/utils/hdrgen/yaml_to_classes.py
index d7a349648340b..14e1f0f32cbbf 100644
--- a/libc/utils/hdrgen/yaml_to_classes.py
+++ b/libc/utils/hdrgen/yaml_to_classes.py
@@ -37,6 +37,7 @@ def yaml_to_classes(yaml_data, header_class, entry_points=None):
     header = header_class(header_name)
     header.template_file = yaml_data.get("header_template")
     header.standards = yaml_data.get("standards", [])
+    header.merge_yaml_files = yaml_data.get("merge_yaml_files", [])
 
     for macro_data in yaml_data.get("macros", []):
         header.add_macro(
@@ -126,7 +127,7 @@ def load_yaml_file(yaml_file, header_class, entry_points):
     Returns:
         HeaderFile: An instance of HeaderFile populated with the data.
     """
-    with open(yaml_file, "r") as f:
+    with yaml_file.open() as f:
         yaml_data = yaml.safe_load(f)
     return yaml_to_classes(yaml_data, header_class, entry_points)
 
@@ -264,7 +265,7 @@ def main():
         add_function_to_yaml(args.yaml_file, args.add_function)
 
     header_class = GpuHeader if args.export_decls else HeaderFile
-    header = load_yaml_file(args.yaml_file, header_class, args.entry_points)
+    header = load_yaml_file(Path(args.yaml_file), header_class, args.entry_points)
 
     header_str = str(header)