diff --git a/src/registrar/config/settings.py b/src/registrar/config/settings.py
index e272e6622..933d95828 100644
--- a/src/registrar/config/settings.py
+++ b/src/registrar/config/settings.py
@@ -523,6 +523,9 @@ STATIC_URL = "public/"
 # {% public_site_url subdir/path %} template tag
 GETGOV_PUBLIC_SITE_URL = env_getgov_public_site_url
 
+# Base URL of application
+BASE_URL = env_base_url
+
 # endregion
 # region: Registry----------------------------------------------------------###
 
diff --git a/src/registrar/management/commands/generate_test_transition_domains.py b/src/registrar/management/commands/generate_test_transition_domains.py
new file mode 100644
index 000000000..911857a1c
--- /dev/null
+++ b/src/registrar/management/commands/generate_test_transition_domains.py
@@ -0,0 +1,60 @@
+"""Data migration: Generate fake transition domains, replacing existing ones."""
+
+import logging
+
+from django.core.management import BaseCommand
+from registrar.models import TransitionDomain, Domain
+
+logger = logging.getLogger(__name__)
+
+
+class Command(BaseCommand):
+    help = "Generate test transition domains from existing domains"
+
+    # Generates test transition domains for testing send_domain_invitations script.
+    # Running this script removes all existing transition domains, so use with caution.
+    # Transition domains are created with email addresses provided as command line
+    # argument. Email addresses for testing are passed as comma delimited list of
+    # email addresses, and are required to be provided.  Email addresses from the list
+    # are assigned to transition domains at time of creation.
+
+    def add_arguments(self, parser):
+        """Add command line arguments."""
+        parser.add_argument(
+            "-e",
+            "--emails",
+            required=True,
+            dest="emails",
+            help="Comma-delimited list of email addresses to be used for testing",
+        )
+
+    def handle(self, **options):
+        """Delete existing TransitionDomains.  Generate test ones."""
+
+        # split options[emails] into an array of test emails
+        test_emails = options["emails"].split(",")
+
+        # setting up test data
+        self.delete_test_transition_domains()
+        self.load_test_transition_domains(test_emails)
+
+    def load_test_transition_domains(self, test_emails):
+        """Load test transition domains"""
+
+        # counter for test_emails index
+        test_emails_counter = 0
+        # Need to get actual domain names from the database for this test
+        real_domains = Domain.objects.all()
+        for real_domain in real_domains:
+            TransitionDomain.objects.create(
+                username=test_emails[test_emails_counter % len(test_emails)],
+                domain_name=real_domain.name,
+                status="created",
+                email_sent=False,
+            )
+            test_emails_counter += 1
+
+    def delete_test_transition_domains(self):
+        self.transition_domains = TransitionDomain.objects.all()
+        for transition_domain in self.transition_domains:
+            transition_domain.delete()
diff --git a/src/registrar/management/commands/send_domain_invitations.py b/src/registrar/management/commands/send_domain_invitations.py
new file mode 100644
index 000000000..3f3542c70
--- /dev/null
+++ b/src/registrar/management/commands/send_domain_invitations.py
@@ -0,0 +1,148 @@
+"""Data migration: Send domain invitations once to existing customers."""
+
+import logging
+import copy
+
+from django.conf import settings
+from django.core.management import BaseCommand
+from django.urls import reverse
+from registrar.models import TransitionDomain, Domain
+from ...utility.email import send_templated_email, EmailSendingError
+from typing import List
+
+logger = logging.getLogger(__name__)
+
+
+class Command(BaseCommand):
+    help = "Send domain invitations once to existing customers."
+
+    # this array is used to store and process the transition_domains
+    transition_domains: List[str] = []
+    # this array is used to store domains with errors, which are not
+    # sent emails; this array is used to update the succesful
+    # transition_domains to email_sent=True, and also to report
+    # out errors
+    domains_with_errors: List[str] = []
+    # this array is used to store email_context; each item in the array
+    # contains the context for a single email; single emails may be 1
+    # or more transition_domains, as they are grouped by username
+    emails_to_send: List[str] = []
+
+    def add_arguments(self, parser):
+        """Add command line arguments."""
+        parser.add_argument(
+            "-s",
+            "--send_emails",
+            action="store_true",
+            default=False,
+            dest="send_emails",
+            help="Send emails ",
+        )
+
+    def handle(self, **options):
+        """Process the objects in TransitionDomain."""
+
+        logger.debug("checking domains and preparing emails")
+        # Get all TransitionDomain objects
+        self.transition_domains = TransitionDomain.objects.filter(
+            email_sent=False,
+        ).order_by("username")
+
+        self.build_emails_to_send_array()
+
+        if options["send_emails"]:
+            logger.debug("about to send emails")
+            self.send_emails()
+            logger.debug("done sending emails")
+
+            self.update_domains_as_sent()
+
+            logger.debug("done sending emails and updating transition_domains")
+        else:
+            logger.debug("not sending emails")
+
+    def build_emails_to_send_array(self):
+        """this method sends emails to distinct usernames"""
+
+        # data structure to hold email context for a single email;
+        # transition_domains ordered by username, a single email_context
+        # may include information from more than one transition_domain
+        email_context = {"email": ""}
+
+        # loop through all transition_domains; group them by username
+        # into emails_to_send_array
+        for transition_domain in self.transition_domains:
+            # attempt to get the domain from domain objects; if there is
+            # an error getting the domain, skip this domain and add it to
+            # domains_with_errors
+            try:
+                domain = Domain.objects.get(name=transition_domain.domain_name)
+                # if prior username does not match current username
+                if (
+                    not email_context["email"]
+                    or email_context["email"] != transition_domain.username
+                ):
+                    # if not first in list of transition_domains
+                    if email_context["email"]:
+                        # append the email context to the emails_to_send array
+                        self.emails_to_send.append(copy.deepcopy(email_context))
+                    email_context["domains"] = []
+                email_context["email"] = transition_domain.username
+                email_context["domains"].append(
+                    {
+                        "name": transition_domain.domain_name,
+                        "url": settings.BASE_URL
+                        + reverse("domain", kwargs={"pk": domain.id}),
+                    }
+                )
+            except Exception as err:
+                # error condition if domain not in database
+                self.domains_with_errors.append(
+                    copy.deepcopy(transition_domain.domain_name)
+                )
+                logger.error(
+                    f"error retrieving domain {transition_domain.domain_name}: {err}"
+                )
+        # if there are at least one more transition domains than errors,
+        # then send one more
+        if len(self.transition_domains) > len(self.domains_with_errors):
+            self.emails_to_send.append(email_context)
+
+    def send_emails(self):
+        for email_data in self.emails_to_send:
+            self.send_email(email_data)
+
+    def send_email(self, email_data):
+        try:
+            send_templated_email(
+                "emails/transition_domain_invitation.txt",
+                "emails/transition_domain_invitation_subject.txt",
+                to_address=email_data["email"],
+                context={
+                    "domains": email_data["domains"],
+                },
+            )
+            # if log level set to debug, success message is logged
+            logger.debug(
+                f"email sent successfully to {email_data['email']} for "
+                f"{[domain['name'] for domain in email_data['domains']]}"
+            )
+        except EmailSendingError as err:
+            logger.error(
+                f"email did not send successfully to {email_data['email']} "
+                f"for {[domain['name'] for domain in email_data['domains']]}"
+                f": {err}"
+            )
+            # if email failed to send, set error in domains_with_errors for each
+            # domain in the email so that transition domain email_sent is not set
+            # to True
+            for domain in email_data["domains"]:
+                self.domains_with_errors.append(domain)
+
+    def update_domains_as_sent(self):
+        """set email_sent to True in all transition_domains which have
+        been processed successfully"""
+        for transition_domain in self.transition_domains:
+            if transition_domain.domain_name not in self.domains_with_errors:
+                transition_domain.email_sent = True
+                transition_domain.save()
diff --git a/src/registrar/templates/emails/transition_domain_invitation.txt b/src/registrar/templates/emails/transition_domain_invitation.txt
new file mode 100644
index 000000000..8b7389c04
--- /dev/null
+++ b/src/registrar/templates/emails/transition_domain_invitation.txt
@@ -0,0 +1,11 @@
+You have been invited to manage {% if domains|length > 1 %}multiple domains{% else %}the domain {{ domains.0.name }}{% endif %} on get.gov, 
+the registrar for .gov domain names.
+{%if domains|length > 1 %}
+To accept your invitation, go to each of the following urls:
+ {% for domain in domains %}
+  {{ domain.url }} (to manage {{ domain.name }})
+ {% endfor %}
+{% else %}
+To accept your invitation, go to <{{ domains.0.url }}>.
+{% endif %}
+You will need to log in with a Login.gov account using this email address.
diff --git a/src/registrar/templates/emails/transition_domain_invitation_subject.txt b/src/registrar/templates/emails/transition_domain_invitation_subject.txt
new file mode 100644
index 000000000..380b338b2
--- /dev/null
+++ b/src/registrar/templates/emails/transition_domain_invitation_subject.txt
@@ -0,0 +1 @@
+You are invited to manage {% if domains|length > 1 %}multiple domains{% else %}{{ domains.0 }}{% endif %} on get.gov