diff --git a/.changelog/23127.txt b/.changelog/23127.txt
new file mode 100644
index 00000000000..eac80665995
--- /dev/null
+++ b/.changelog/23127.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_vpn_connection: Add support for `ipsec.1-aes256` connection type
+```
\ No newline at end of file
diff --git a/internal/service/ec2/enum.go b/internal/service/ec2/enum.go
index da23215e138..8e7c9c83903 100644
--- a/internal/service/ec2/enum.go
+++ b/internal/service/ec2/enum.go
@@ -161,12 +161,14 @@ func VpnTunnelOptionsStartupAction_Values() []string {
 }
 
 const (
-	VpnConnectionTypeIpsec1 = "ipsec.1"
+	VpnConnectionTypeIpsec1        = "ipsec.1"
+	VpnConnectionTypeIpsec1_AES256 = "ipsec.1-aes256" // https://github.com/hashicorp/terraform-provider-aws/issues/23105.
 )
 
 func VpnConnectionType_Values() []string {
 	return []string{
 		VpnConnectionTypeIpsec1,
+		VpnConnectionTypeIpsec1_AES256,
 	}
 }