diff --git a/lib/ansible/modules/network/aci/mso_schema_site_bd_subnet.py b/lib/ansible/modules/network/aci/mso_schema_site_bd_subnet.py
new file mode 100644
index 00000000000..2dd12855b72
--- /dev/null
+++ b/lib/ansible/modules/network/aci/mso_schema_site_bd_subnet.py
@@ -0,0 +1,262 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+# Copyright: (c) 2019, Dag Wieers (@dagwieers) <dag@wieers.com>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+ANSIBLE_METADATA = {'metadata_version': '1.1',
+                    'status': ['preview'],
+                    'supported_by': 'community'}
+
+DOCUMENTATION = r'''
+---
+module: mso_schema_site_bd_subnet
+short_description: Manage site BD subnets in schema template
+description:
+- Manage site BD subnets in schema template on Cisco ACI Multi-Site.
+author:
+- Dag Wieers (@dagwieers)
+version_added: '2.8'
+options:
+  schema:
+    description:
+    - The name of the schema.
+    type: str
+    required: yes
+  site:
+    description:
+    - The name of the site.
+    type: str
+    required: yes
+  template:
+    description:
+    - The name of the template.
+    type: str
+    required: yes
+  bd:
+    description:
+    - The name of the BD.
+    type: str
+    aliases: [ name ]
+  subnet:
+    description:
+    - The IP range in CIDR notation.
+    type: str
+    required: true
+    aliases: [ ip ]
+  description:
+    description:
+    - The description of this subnet.
+    type: str
+  scope:
+    description:
+    - The scope of the subnet.
+    type: str
+    choices: [ private, public ]
+  shared:
+    description:
+    - Whether this subnet is shared between VRFs.
+    type: bool
+  no_default_gateway:
+    description:
+    - Whether this subnet has a default gateway.
+    type: bool
+  state:
+    description:
+    - Use C(present) or C(absent) for adding or removing.
+    - Use C(query) for listing an object or multiple objects.
+    type: str
+    choices: [ absent, present, query ]
+    default: present
+seealso:
+- module: mso_schema_site_bd
+- module: mso_schema_template_bd
+extends_documentation_fragment: mso
+'''
+
+EXAMPLES = r'''
+- name: Add a new site BD subnet
+  mso_schema_site_bd_subnet:
+    host: mso_host
+    username: admin
+    password: SomeSecretPassword
+    schema: Schema1
+    site: Site1
+    template: Template1
+    bd: BD1
+    subnet: 11.11.11.0/24
+    state: present
+  delegate_to: localhost
+
+- name: Remove a site BD subnet
+  mso_schema_site_bd_subnet:
+    host: mso_host
+    username: admin
+    password: SomeSecretPassword
+    schema: Schema1
+    site: Site1
+    template: Template1
+    bd: BD1
+    subnet: 11.11.11.0/24
+    state: absent
+  delegate_to: localhost
+
+- name: Query a specific site BD subnet
+  mso_schema_site_bd_subnet:
+    host: mso_host
+    username: admin
+    password: SomeSecretPassword
+    schema: Schema1
+    site: Site1
+    template: Template1
+    bd: BD1
+    subnet: 11.11.11.0/24
+    state: query
+  delegate_to: localhost
+  register: query_result
+
+- name: Query all site BD subnets
+  mso_schema_site_bd_subnet:
+    host: mso_host
+    username: admin
+    password: SomeSecretPassword
+    schema: Schema1
+    site: Site1
+    template: Template1
+    bd: BD1
+    state: query
+  delegate_to: localhost
+  register: query_result
+'''
+
+RETURN = r'''
+'''
+
+from ansible.module_utils.basic import AnsibleModule
+from ansible.module_utils.network.aci.mso import MSOModule, mso_argument_spec, mso_subnet_spec
+
+
+def main():
+    argument_spec = mso_argument_spec()
+    argument_spec.update(
+        schema=dict(type='str', required=True),
+        site=dict(type='str', required=True),
+        template=dict(type='str', required=True),
+        bd=dict(type='str', aliases=['name']),  # This parameter is not required for querying all objects
+        state=dict(type='str', default='present', choices=['absent', 'present', 'query']),
+    )
+    argument_spec.update(mso_subnet_spec())
+
+    module = AnsibleModule(
+        argument_spec=argument_spec,
+        supports_check_mode=True,
+        required_if=[
+            ['state', 'absent', ['bd']],
+            ['state', 'present', ['bd']],
+        ],
+    )
+
+    schema = module.params['schema']
+    site = module.params['site']
+    template = module.params['template']
+    bd = module.params['bd']
+    subnet = module.params['subnet']
+    description = module.params['description']
+    scope = module.params['scope']
+    shared = module.params['shared']
+    no_default_gateway = module.params['no_default_gateway']
+    state = module.params['state']
+
+    mso = MSOModule(module)
+
+    # Get schema_id
+    schema_obj = mso.get_obj('schemas', displayName=schema)
+    if not schema_obj:
+        mso.fail_json(msg="Provided schema '{0}' does not exist".format(schema))
+
+    schema_path = 'schemas/{id}'.format(**schema_obj)
+    schema_id = schema_obj['id']
+
+    # Get site
+    site_id = mso.lookup_site(site)
+
+    # Get site_idx
+    sites = [(s['siteId'], s['templateName']) for s in schema_obj['sites']]
+    if (site_id, template) not in sites:
+        mso.fail_json(msg="Provided site/template '{0}-{1}' does not exist. Existing sites/templates: {2}".format(site, template, ', '.join(sites)))
+
+    # Schema-access uses indexes
+    site_idx = sites.index((site_id, template))
+    # Path-based access uses site_id-template
+    site_template = '{0}-{1}'.format(site_id, template)
+
+    # Get BD
+    bd_ref = mso.bd_ref(schema_id=schema_id, template=template, bd=bd)
+    bds = [v['bdRef'] for v in schema_obj['sites'][site_idx]['bds']]
+    if bd_ref not in bds:
+        mso.fail_json(msg="Provided BD '{0}' does not exist. Existing BDs: {1}".format(bd, ', '.join(bds)))
+    bd_idx = bds.index(bd_ref)
+
+    # Get Subnet
+    subnets = [s['ip'] for s in schema_obj['sites'][site_idx]['bds'][bd_idx]['subnets']]
+    if subnet in subnets:
+        subnet_idx = subnets.index(subnet)
+        # FIXME: Changes based on index are DANGEROUS
+        subnet_path = '/sites/{0}/bds/{1}/subnets/{2}'.format(site_template, bd, subnet_idx)
+        mso.existing = schema_obj['sites'][site_idx]['bds'][bd_idx]['subnets'][subnet_idx]
+
+    if state == 'query':
+        if subnet is None:
+            mso.existing = schema_obj['sites'][site_idx]['bds'][bd_idx]['subnets']
+        elif not mso.existing:
+            mso.fail_json(msg="Subnet IP '{subnet}' not found".format(subnet=subnet))
+        mso.exit_json()
+
+    subnets_path = '/sites/{0}/bds/{1}/subnets'.format(site_template, bd)
+    ops = []
+
+    mso.previous = mso.existing
+    if state == 'absent':
+        if mso.existing:
+            mso.sent = mso.existing = {}
+            ops.append(dict(op='remove', path=subnet_path))
+
+    elif state == 'present':
+        if not mso.existing:
+            if description is None:
+                description = subnet
+            if scope is None:
+                scope = 'private'
+            if shared is None:
+                shared = False
+            if no_default_gateway is None:
+                no_default_gateway = False
+
+        payload = dict(
+            ip=subnet,
+            description=description,
+            scope=scope,
+            shared=shared,
+            noDefaultGateway=no_default_gateway,
+        )
+
+        mso.sanitize(payload, collate=True)
+
+        if mso.existing:
+            ops.append(dict(op='replace', path=subnet_path, value=mso.sent))
+        else:
+            ops.append(dict(op='add', path=subnets_path + '/-', value=mso.sent))
+
+        mso.existing = mso.proposed
+
+    if not module.check_mode:
+        mso.request(schema_path, method='PATCH', data=ops)
+
+    mso.exit_json()
+
+
+if __name__ == "__main__":
+    main()