diff --git a/sbin/ifconfig/af_inet6.c b/sbin/ifconfig/af_inet6.c
--- a/sbin/ifconfig/af_inet6.c
+++ b/sbin/ifconfig/af_inet6.c
@@ -706,6 +706,8 @@
 	DEF_CMD("-accept_rtadv",-ND6_IFF_ACCEPT_RTADV,	setnd6flags),
 	DEF_CMD("no_radr",	ND6_IFF_NO_RADR,	setnd6flags),
 	DEF_CMD("-no_radr",	-ND6_IFF_NO_RADR,	setnd6flags),
+	DEF_CMD("no_prefixaddr",ND6_IFF_NO_PREFIXADDR,	setnd6flags),
+	DEF_CMD("-no_prefixaddr",-ND6_IFF_NO_PREFIXADDR,setnd6flags),
 	DEF_CMD("defaultif",	1,			setnd6defif),
 	DEF_CMD("-defaultif",	-1,			setnd6defif),
 	DEF_CMD("ifdisabled",	ND6_IFF_IFDISABLED,	setnd6flags),
diff --git a/sbin/ifconfig/af_nd6.c b/sbin/ifconfig/af_nd6.c
--- a/sbin/ifconfig/af_nd6.c
+++ b/sbin/ifconfig/af_nd6.c
@@ -66,6 +66,7 @@
 	[9]  = "IPV6_ONLY",
 	[10] = "IPV6_ONLY_MANUAL",
 #endif
+	[11] = "NO_PREFIXADDR",
 	[15] = "DEFAULTIF",
 };
 
diff --git a/sbin/ifconfig/ifconfig.8 b/sbin/ifconfig/ifconfig.8
--- a/sbin/ifconfig/ifconfig.8
+++ b/sbin/ifconfig/ifconfig.8
@@ -28,7 +28,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd April 24, 2025
+.Dd May 2, 2025
 .Dt IFCONFIG 8
 .Os
 .Sh NAME
@@ -952,8 +952,32 @@
 .Va net.inet6.ip6.no_radr
 controls whether this flag is set by default or not.
 .It Cm -no_radr
-Clear a flag
-.Cm no_radr .
+Clear the
+.Cm no_radr
+flag.
+.It Cm no_prefixaddr
+Set a flag to control whether a Router Advertisement message including
+an on-link autonomous prefix will result in an IP address in that prefix
+being configured automatically.
+If this flag is set, an address will not be configured, but a route for
+the on-link prefix will be added to the system routing table.
+In this case, the administrator should configure a static IP address.
+The advertised router will still be added to the Default Router List
+unless the
+.Cm no_radr
+flag is also set.
+When the
+.Cm accept_rtadv
+flag is disabled, this flag has no effect.
+The
+.Xr sysctl 8
+variable
+.Va net.inet6.ip6.no_prefixaddr
+controls whether this flag is set by default or not.
+.It Cm -no_prefixaddr
+Clear the
+.Cm no_prefixaddr
+flag.
 .It Cm auto_linklocal
 Set a flag to perform automatic link-local address configuration when
 the interface becomes available.
diff --git a/sys/netinet6/in6_proto.c b/sys/netinet6/in6_proto.c
--- a/sys/netinet6/in6_proto.c
+++ b/sys/netinet6/in6_proto.c
@@ -155,6 +155,7 @@
 VNET_DEFINE(int, ip6_defmcasthlim) = IPV6_DEFAULT_MULTICAST_HOPS;
 VNET_DEFINE(int, ip6_accept_rtadv) = 0;
 VNET_DEFINE(int, ip6_no_radr) = 0;
+VNET_DEFINE(bool, ip6_no_prefixaddr) = 0;
 VNET_DEFINE(int, ip6_norbit_raif) = 0;
 VNET_DEFINE(int, ip6_rfc6204w3) = 0;
 VNET_DEFINE(int, ip6_hdrnestlimit) = 15;/* How many header options will we
@@ -272,6 +273,10 @@
 	"Default value of per-interface flag to control whether routers "
 	"sending ICMPv6 RA messages on that interface are added into the "
 	"default router list");
+SYSCTL_BOOL(_net_inet6_ip6, OID_AUTO, no_prefixaddr,
+	CTLFLAG_VNET | CTLFLAG_RWTUN, &VNET_NAME(ip6_no_prefixaddr), 0,
+	"Default value of per-interface flag to control whether ICMPv6 RA "
+	"messages with a prefix should configure an interface address");
 SYSCTL_INT(_net_inet6_ip6, IPV6CTL_NORBIT_RAIF, norbit_raif,
 	CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip6_norbit_raif), 0,
 	"Always set clear the R flag in ICMPv6 NA messages when accepting RA "
diff --git a/sys/netinet6/ip6_input.c b/sys/netinet6/ip6_input.c
--- a/sys/netinet6/ip6_input.c
+++ b/sys/netinet6/ip6_input.c
@@ -230,6 +230,7 @@
 	    &V_ip6_auto_linklocal);
 	TUNABLE_INT_FETCH("net.inet6.ip6.accept_rtadv", &V_ip6_accept_rtadv);
 	TUNABLE_INT_FETCH("net.inet6.ip6.no_radr", &V_ip6_no_radr);
+	TUNABLE_BOOL_FETCH("net.inet6.ip6.no_prefixaddr", &V_ip6_no_prefixaddr);
 
 	CK_STAILQ_INIT(&V_in6_ifaddrhead);
 	V_in6_ifaddrhashtbl = hashinit(IN6ADDR_NHASH, M_IFADDR,
diff --git a/sys/netinet6/ip6_var.h b/sys/netinet6/ip6_var.h
--- a/sys/netinet6/ip6_var.h
+++ b/sys/netinet6/ip6_var.h
@@ -313,6 +313,7 @@
 VNET_DECLARE(int, ip6_sendredirects);	/* send IP redirects when forwarding? */
 VNET_DECLARE(int, ip6_accept_rtadv);	/* Acts as a host not a router */
 VNET_DECLARE(int, ip6_no_radr);		/* No defroute from RA */
+VNET_DECLARE(bool, ip6_no_prefixaddr);	/* No address from RA */
 VNET_DECLARE(int, ip6_norbit_raif);	/* Disable R-bit in NA on RA
 					 * receiving IF. */
 VNET_DECLARE(int, ip6_rfc6204w3);	/* Accept defroute from RA even when
@@ -324,6 +325,7 @@
 #define	V_ip6_sendredirects		VNET(ip6_sendredirects)
 #define	V_ip6_accept_rtadv		VNET(ip6_accept_rtadv)
 #define	V_ip6_no_radr			VNET(ip6_no_radr)
+#define	V_ip6_no_prefixaddr		VNET(ip6_no_prefixaddr)
 #define	V_ip6_norbit_raif		VNET(ip6_norbit_raif)
 #define	V_ip6_rfc6204w3			VNET(ip6_rfc6204w3)
 #define	V_ip6_hdrnestlimit		VNET(ip6_hdrnestlimit)
diff --git a/sys/netinet6/nd6.h b/sys/netinet6/nd6.h
--- a/sys/netinet6/nd6.h
+++ b/sys/netinet6/nd6.h
@@ -95,6 +95,7 @@
 #define	ND6_IFF_IPV6_ONLY_MANUAL	0x400
 #define	ND6_IFF_IPV6_ONLY_MASK	(ND6_IFF_IPV6_ONLY|ND6_IFF_IPV6_ONLY_MANUAL)
 #endif
+#define	ND6_IFF_NO_PREFIXADDR	0x800
 
 #ifdef _KERNEL
 #define ND_IFINFO(ifp) \
diff --git a/sys/netinet6/nd6.c b/sys/netinet6/nd6.c
--- a/sys/netinet6/nd6.c
+++ b/sys/netinet6/nd6.c
@@ -318,8 +318,12 @@
 			/* If we globally accept rtadv, assume IPv6 on. */
 			nd->flags &= ~ND6_IFF_IFDISABLED;
 	}
-	if (V_ip6_no_radr && !(ifp->if_flags & IFF_LOOPBACK))
-		nd->flags |= ND6_IFF_NO_RADR;
+	if ((ifp->if_flags & IFF_LOOPBACK) == 0) {
+		if (V_ip6_no_radr)
+			nd->flags |= ND6_IFF_NO_RADR;
+		if (V_ip6_no_prefixaddr)
+			nd->flags |= ND6_IFF_NO_PREFIXADDR;
+	}
 
 	/* XXX: we cannot call nd6_setmtu since ifp is not fully initialized */
 	nd6_setmtu0(ifp, nd);
diff --git a/sys/netinet6/nd6_rtr.c b/sys/netinet6/nd6_rtr.c
--- a/sys/netinet6/nd6_rtr.c
+++ b/sys/netinet6/nd6_rtr.c
@@ -1711,6 +1711,15 @@
 	}
 	if (ia6_match == NULL && new->ndpr_vltime) {
 		int ifidlen;
+		struct nd_ifinfo *ndi = ND_IFINFO(ifp);
+
+		/*
+		 * If no_prefixaddr is set, skip creating a new address.  Do
+		 * this here after we've already processed any addresses that
+		 * might already exist.
+		 */
+		if (ndi->flags & ND6_IFF_NO_PREFIXADDR)
+			goto end;
 
 		/*
 		 * 5.5.3 (d) (continued)