diff --git a/cyclonedx/_internal/__init__.py b/cyclonedx/_internal/__init__.py
index 4513dbac..c0943da5 100644
--- a/cyclonedx/_internal/__init__.py
+++ b/cyclonedx/_internal/__init__.py
@@ -20,3 +20,14 @@
 !!! ALL SYMBOLS IN HERE ARE INTERNAL.
 Everything might change without any notice.
 """
+
+from typing import Optional, Union
+
+from ..model.bom_ref import BomRef
+
+
+def bom_ref_from_str(bom_ref: Optional[Union[str, BomRef]]) -> BomRef:
+    if isinstance(bom_ref, BomRef):
+        return bom_ref
+    else:
+        return BomRef(value=str(bom_ref) if bom_ref else None)
diff --git a/cyclonedx/model/bom.py b/cyclonedx/model/bom.py
index 7bd09740..c4478ac1 100644
--- a/cyclonedx/model/bom.py
+++ b/cyclonedx/model/bom.py
@@ -41,6 +41,7 @@
 from .bom_ref import BomRef
 from .component import Component
 from .contact import OrganizationalContact, OrganizationalEntity
+from .definition import DefinitionRepository
 from .dependency import Dependable, Dependency
 from .license import License, LicenseExpression, LicenseRepository
 from .service import Service
@@ -317,6 +318,7 @@ def __init__(
         dependencies: Optional[Iterable[Dependency]] = None,
         vulnerabilities: Optional[Iterable[Vulnerability]] = None,
         properties: Optional[Iterable[Property]] = None,
+        definitions: Optional[DefinitionRepository] = None,
     ) -> None:
         """
         Create a new Bom that you can manually/programmatically add data to later.
@@ -333,6 +335,7 @@ def __init__(
         self.vulnerabilities = vulnerabilities or []  # type:ignore[assignment]
         self.dependencies = dependencies or []  # type:ignore[assignment]
         self.properties = properties or []  # type:ignore[assignment]
+        self.definitions = definitions or DefinitionRepository()
 
     @property
     @serializable.type_mapping(UrnUuidHelper)
@@ -520,6 +523,22 @@ def vulnerabilities(self) -> 'SortedSet[Vulnerability]':
     def vulnerabilities(self, vulnerabilities: Iterable[Vulnerability]) -> None:
         self._vulnerabilities = SortedSet(vulnerabilities)
 
+    @property
+    @serializable.view(SchemaVersion1Dot6)
+    @serializable.xml_sequence(90)
+    def definitions(self) -> Optional[DefinitionRepository]:
+        """
+        The repository for definitions
+
+        Returns:
+            `DefinitionRepository`
+        """
+        return self._definitions if len(self._definitions) > 0 else None
+
+    @definitions.setter
+    def definitions(self, definitions: DefinitionRepository) -> None:
+        self._definitions = definitions
+
     # @property
     # ...
     # @serializable.view(SchemaVersion1Dot5)
diff --git a/cyclonedx/model/definition.py b/cyclonedx/model/definition.py
new file mode 100644
index 00000000..66a2edbc
--- /dev/null
+++ b/cyclonedx/model/definition.py
@@ -0,0 +1,244 @@
+# This file is part of CycloneDX Python Library
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+# Copyright (c) OWASP Foundation. All Rights Reserved.
+
+from typing import TYPE_CHECKING, Any, Iterable, Optional, Union
+
+import serializable
+from sortedcontainers import SortedSet
+
+from .._internal import bom_ref_from_str
+from .._internal.compare import ComparableTuple as _ComparableTuple
+from ..serialization import BomRefHelper
+from . import ExternalReference
+from .bom_ref import BomRef
+
+if TYPE_CHECKING:  # pragma: no cover
+    pass
+
+
+@serializable.serializable_class(serialization_types=[
+    serializable.SerializationType.JSON,
+    serializable.SerializationType.XML]
+)
+class Standard:
+    """
+    A standard of regulations, industry or organizational-specific standards, maturity models, best practices,
+    or any other requirements.
+    """
+
+    def __init__(
+        self, *,
+        bom_ref: Optional[Union[str, BomRef]] = None,
+        name: Optional[str] = None,
+        version: Optional[str] = None,
+        description: Optional[str] = None,
+        owner: Optional[str] = None,
+        external_references: Optional[Iterable['ExternalReference']] = None
+    ) -> None:
+        self._bom_ref = bom_ref_from_str(bom_ref)
+        self.name = name
+        self.version = version
+        self.description = description
+        self.owner = owner
+        self.external_references = external_references or []  # type:ignore[assignment]
+
+    def __lt__(self, other: Any) -> bool:
+        if isinstance(other, Standard):
+            return (_ComparableTuple((self.bom_ref, self.name, self.version))
+                    < _ComparableTuple((other.bom_ref, other.name, other.version)))
+        return NotImplemented
+
+    def __eq__(self, other: object) -> bool:
+        if isinstance(other, Standard):
+            return hash(other) == hash(self)
+        return False
+
+    def __hash__(self) -> int:
+        return hash((
+            self.bom_ref, self.name, self.version, self.description, self.owner, tuple(self.external_references)
+        ))
+
+    def __repr__(self) -> str:
+        return f'<Standard bom-ref={self.bom_ref}, name={self.name}, version={self.version}, ' \
+               f'description={self.description}, owner={self.owner}>'
+
+    @property
+    @serializable.json_name('bom-ref')
+    @serializable.type_mapping(BomRefHelper)
+    @serializable.xml_attribute()
+    @serializable.xml_name('bom-ref')
+    def bom_ref(self) -> BomRef:
+        """
+        An optional identifier which can be used to reference the standard elsewhere in the BOM. Every bom-ref MUST be
+        unique within the BOM. If a value was not provided in the constructor, a UUIDv4 will have been assigned.
+        Returns:
+            `BomRef`
+        """
+        return self._bom_ref
+
+    @property
+    @serializable.xml_string(serializable.XmlStringSerializationType.NORMALIZED_STRING)
+    @serializable.xml_sequence(2)
+    def name(self) -> Optional[str]:
+        """
+        Returns:
+            The name of the standard
+        """
+        return self._name
+
+    @name.setter
+    def name(self, name: Optional[str]) -> None:
+        self._name = name
+
+    @property
+    @serializable.xml_string(serializable.XmlStringSerializationType.NORMALIZED_STRING)
+    @serializable.xml_sequence(3)
+    def version(self) -> Optional[str]:
+        """
+        Returns:
+            The version of the standard
+        """
+        return self._version
+
+    @version.setter
+    def version(self, version: Optional[str]) -> None:
+        self._version = version
+
+    @property
+    @serializable.xml_string(serializable.XmlStringSerializationType.NORMALIZED_STRING)
+    @serializable.xml_sequence(4)
+    def description(self) -> Optional[str]:
+        """
+        Returns:
+            The description of the standard
+        """
+        return self._description
+
+    @description.setter
+    def description(self, description: Optional[str]) -> None:
+        self._description = description
+
+    @property
+    @serializable.xml_string(serializable.XmlStringSerializationType.NORMALIZED_STRING)
+    @serializable.xml_sequence(5)
+    def owner(self) -> Optional[str]:
+        """
+        Returns:
+            The owner of the standard, often the entity responsible for its release.
+        """
+        return self._owner
+
+    @owner.setter
+    def owner(self, owner: Optional[str]) -> None:
+        self._owner = owner
+
+    # @property
+    # @serializable.xml_array(serializable.XmlArraySerializationType.NESTED, 'requirement')
+    # @serializable.xml_sequence(10)
+    # def requirements(self) -> 'SortedSet[Requirement]':
+    #     """
+    #     Returns:
+    #         A SortedSet of requirements comprising the standard.
+    #     """
+    #     return self._requirements
+    #
+    # @requirements.setter
+    # def requirements(self, requirements: Iterable[Requirement]) -> None:
+    #     self._requirements = SortedSet(requirements)
+    #
+    # @property
+    # @serializable.xml_array(serializable.XmlArraySerializationType.NESTED, 'level')
+    # @serializable.xml_sequence(20)
+    # def levels(self) -> 'SortedSet[Level]':
+    #     """
+    #     Returns:
+    #         A SortedSet of levels associated with the standard. Some standards have different levels of compliance.
+    #     """
+    #     return self._levels
+    #
+    # @levels.setter
+    # def levels(self, levels: Iterable[Level]) -> None:
+    #     self._levels = SortedSet(levels)
+
+    @property
+    @serializable.xml_array(serializable.XmlArraySerializationType.NESTED, 'reference')
+    @serializable.xml_sequence(30)
+    def external_references(self) -> 'SortedSet[ExternalReference]':
+        """
+        Returns:
+            A SortedSet of external references associated with the standard.
+        """
+        return self._external_references
+
+    @external_references.setter
+    def external_references(self, external_references: Iterable[ExternalReference]) -> None:
+        self._external_references = SortedSet(external_references)
+
+
+@serializable.serializable_class(name='definitions',
+                                 serialization_types=[
+                                     serializable.SerializationType.JSON,
+                                     serializable.SerializationType.XML]
+                                 )
+class DefinitionRepository:
+    """
+    The repository for definitions
+    """
+
+    def __init__(
+        self, *,
+        standards: Optional[Iterable[Standard]] = None
+    ) -> None:
+        self.standards = standards or ()  # type:ignore[assignment]
+
+    @property
+    @serializable.xml_array(serializable.XmlArraySerializationType.NESTED, 'standard')
+    @serializable.xml_sequence(1)
+    def standards(self) -> 'SortedSet[Standard]':
+        """
+        Returns:
+            A SortedSet of Standards
+        """
+        return self._standards
+
+    @standards.setter
+    def standards(self, standards: Iterable[Standard]) -> None:
+        self._standards = SortedSet(standards)
+
+    def __len__(self) -> int:
+        return len(self._standards)
+
+    def __bool__(self) -> bool:
+        return len(self._standards) > 0
+
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, DefinitionRepository):
+            return False
+
+        return self._standards == other._standards
+
+    def __hash__(self) -> int:
+        return hash((tuple(self._standards)))
+
+    def __lt__(self, other: Any) -> bool:
+        if isinstance(other, DefinitionRepository):
+            return (_ComparableTuple(self._standards)
+                    < _ComparableTuple(other.standards))
+        return NotImplemented
+
+    def __repr__(self) -> str:
+        return '<Definitions>'
diff --git a/tests/test_model_definition_repository.py b/tests/test_model_definition_repository.py
new file mode 100644
index 00000000..5605c058
--- /dev/null
+++ b/tests/test_model_definition_repository.py
@@ -0,0 +1,65 @@
+# This file is part of CycloneDX Python Library
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+# Copyright (c) OWASP Foundation. All Rights Reserved.
+
+
+from unittest import TestCase
+
+from cyclonedx.model.definition import DefinitionRepository, Standard
+
+
+class TestModelDefinitionRepository(TestCase):
+
+    def test_init(self) -> DefinitionRepository:
+        s = Standard(name='test-standard')
+        dr = DefinitionRepository(
+            standards=(s, ),
+        )
+        self.assertIs(s, tuple(dr.standards)[0])
+        return dr
+
+    def test_filled(self) -> None:
+        dr = self.test_init()
+        self.assertEqual(1, len(dr))
+        self.assertTrue(dr)
+
+    def test_empty(self) -> None:
+        dr = DefinitionRepository()
+        self.assertEqual(0, len(dr))
+        self.assertFalse(dr)
+
+    def test_unequal_different_type(self) -> None:
+        dr = DefinitionRepository()
+        self.assertFalse(dr == 'other')
+
+    def test_equal_self(self) -> None:
+        dr = DefinitionRepository()
+        dr.standards.add(Standard(name='my-standard'))
+        self.assertTrue(dr == dr)
+
+    def test_unequal(self) -> None:
+        dr1 = DefinitionRepository()
+        dr1.standards.add(Standard(name='my-standard'))
+        tr2 = DefinitionRepository()
+        self.assertFalse(dr1 == tr2)
+
+    def test_equal(self) -> None:
+        s = Standard(name='my-standard')
+        dr1 = DefinitionRepository()
+        dr1.standards.add(s)
+        tr2 = DefinitionRepository()
+        tr2.standards.add(s)
+        self.assertTrue(dr1 == tr2)