diff --git a/clientapi/routing/register.go b/clientapi/routing/register.go
index 1a41a5243..a92513b8b 100644
--- a/clientapi/routing/register.go
+++ b/clientapi/routing/register.go
@@ -211,9 +211,10 @@ var (
 // previous parameters with the ones supplied. This mean you cannot "build up" request params.
 type registerRequest struct {
 	// registration parameters
-	Password string `json:"password"`
-	Username string `json:"username"`
-	Admin    bool   `json:"admin"`
+	Password   string                       `json:"password"`
+	Username   string                       `json:"username"`
+	ServerName gomatrixserverlib.ServerName `json:"-"`
+	Admin      bool                         `json:"admin"`
 	// user-interactive auth params
 	Auth authDict `json:"auth"`
 
@@ -570,11 +571,14 @@ func Register(
 				JSON: response,
 			}
 		}
-
 	}
 	if resErr := httputil.UnmarshalJSON(reqBody, &r); resErr != nil {
 		return *resErr
 	}
+	r.ServerName = cfg.Matrix.ServerName
+	if l, d, err := cfg.Matrix.SplitLocalID('@', r.Username); err == nil {
+		r.Username, r.ServerName = l, d
+	}
 	if req.URL.Query().Get("kind") == "guest" {
 		return handleGuestRegistration(req, r, cfg, userAPI)
 	}
@@ -589,7 +593,7 @@ func Register(
 	// Auto generate a numeric username if r.Username is empty
 	if r.Username == "" {
 		nreq := &userapi.QueryNumericLocalpartRequest{
-			ServerName: cfg.Matrix.ServerName, // TODO: might not be right
+			ServerName: r.ServerName,
 		}
 		nres := &userapi.QueryNumericLocalpartResponse{}
 		if err := userAPI.QueryNumericLocalpart(req.Context(), nreq, nres); err != nil {
@@ -609,7 +613,7 @@ func Register(
 	case r.Type == authtypes.LoginTypeApplicationService && accessTokenErr == nil:
 		// Spec-compliant case (the access_token is specified and the login type
 		// is correctly set, so it's an appservice registration)
-		if resErr := validateApplicationServiceUsername(r.Username, cfg.Matrix.ServerName); resErr != nil {
+		if resErr := validateApplicationServiceUsername(r.Username, r.ServerName); resErr != nil {
 			return *resErr
 		}
 	case accessTokenErr == nil:
@@ -622,7 +626,7 @@ func Register(
 	default:
 		// Spec-compliant case (neither the access_token nor the login type are
 		// specified, so it's a normal user registration)
-		if resErr := validateUsername(r.Username, cfg.Matrix.ServerName); resErr != nil {
+		if resErr := validateUsername(r.Username, r.ServerName); resErr != nil {
 			return *resErr
 		}
 	}
@@ -1027,6 +1031,16 @@ func RegisterAvailable(
 	if u, l, err := cfg.Matrix.SplitLocalID('@', username); err == nil {
 		username, domain = u, l
 	}
+	for _, v := range cfg.Matrix.VirtualHosts {
+		if v.ServerName == domain && !v.AllowRegistration {
+			return util.JSONResponse{
+				Code: http.StatusForbidden,
+				JSON: jsonerror.Forbidden(
+					fmt.Sprintf("Registration is not allowed on %q", string(v.ServerName)),
+				),
+			}
+		}
+	}
 
 	if err := validateUsername(username, domain); err != nil {
 		return *err
diff --git a/setup/config/config_global.go b/setup/config/config_global.go
index acf610218..c78b5c8d0 100644
--- a/setup/config/config_global.go
+++ b/setup/config/config_global.go
@@ -185,6 +185,9 @@ type VirtualHost struct {
 	// by remote servers.
 	// Defaults to 24 hours.
 	KeyValidityPeriod time.Duration `yaml:"key_validity_period"`
+
+	// Is registration enabled on this virtual host?
+	AllowRegistration bool `json:"allow_registration"`
 }
 
 func (v *VirtualHost) Verify(configErrs *ConfigErrors) {