diff --git a/Makefile.dep b/Makefile.dep
index f596f883f685..802f98b2aa5c 100644
--- a/Makefile.dep
+++ b/Makefile.dep
@@ -57,6 +57,10 @@ ifneq (,$(filter gnrc_conn_udp,$(USEMODULE)))
   USEMODULE += gnrc_udp
 endif
 
+ifneq (,$(filter gnrc_netapi_mbox,$(USEMODULE)))
+  USEMODULE += core_mbox
+endif
+
 ifneq (,$(filter netdev2_tap,$(USEMODULE)))
   USEMODULE += netif
   USEMODULE += netdev2_eth
diff --git a/Makefile.pseudomodules b/Makefile.pseudomodules
index 9e02789345f0..27976a1dab9b 100644
--- a/Makefile.pseudomodules
+++ b/Makefile.pseudomodules
@@ -12,6 +12,8 @@ PSEUDOMODULES += gnrc_ipv6_router
 PSEUDOMODULES += gnrc_ipv6_router_default
 PSEUDOMODULES += gnrc_netdev_default
 PSEUDOMODULES += gnrc_neterr
+PSEUDOMODULES += gnrc_netapi_callbacks
+PSEUDOMODULES += gnrc_netapi_mbox
 PSEUDOMODULES += gnrc_pktbuf
 PSEUDOMODULES += gnrc_sixlowpan_border_router_default
 PSEUDOMODULES += gnrc_sixlowpan_default
diff --git a/examples/gnrc_networking/udp.c b/examples/gnrc_networking/udp.c
index a422934e48a0..f7619a8fc3fa 100644
--- a/examples/gnrc_networking/udp.c
+++ b/examples/gnrc_networking/udp.c
@@ -94,7 +94,7 @@ static void start_server(char *port_str)
     uint16_t port;
 
     /* check if server is already running */
-    if (server.pid != KERNEL_PID_UNDEF) {
+    if (server.target.pid != KERNEL_PID_UNDEF) {
         printf("Error: server already running on port %" PRIu32 "\n",
                server.demux_ctx);
         return;
@@ -106,7 +106,7 @@ static void start_server(char *port_str)
         return;
     }
     /* start server (which means registering pktdump for the chosen port) */
-    server.pid = gnrc_pktdump_pid;
+    server.target.pid = gnrc_pktdump_pid;
     server.demux_ctx = (uint32_t)port;
     gnrc_netreg_register(GNRC_NETTYPE_UDP, &server);
     printf("Success: started UDP server on port %" PRIu16 "\n", port);
@@ -115,13 +115,13 @@ static void start_server(char *port_str)
 static void stop_server(void)
 {
     /* check if server is running at all */
-    if (server.pid == KERNEL_PID_UNDEF) {
+    if (server.target.pid == KERNEL_PID_UNDEF) {
         printf("Error: server was not running\n");
         return;
     }
     /* stop server */
     gnrc_netreg_unregister(GNRC_NETTYPE_UDP, &server);
-    server.pid = KERNEL_PID_UNDEF;
+    server.target.pid = KERNEL_PID_UNDEF;
     puts("Success: stopped UDP server");
 }
 
diff --git a/sys/include/net/gnrc/netapi.h b/sys/include/net/gnrc/netapi.h
index 52ce4ae7a945..25dc2a41dd73 100644
--- a/sys/include/net/gnrc/netapi.h
+++ b/sys/include/net/gnrc/netapi.h
@@ -21,6 +21,36 @@
  * @file
  * @brief       Generic interface to communicate with GNRC modules
  *
+ * @defgroup    net_gnrc_netapi_mbox   Mailbox IPC extension
+ * @ingroup     net_gnrc_netapi
+ * @brief       @ref core_mbox "Mailbox IPC" extension for @ref net_gnrc_netapi
+ * @{
+ *
+ * @details The submodule `gnrc_netapi_mbox` provides an extension for
+ *          @ref core_mbox "Mailbox IPC".
+ *
+ * To use, add the module `gnrc_netapi_mbox` to the `USEMODULE` macro in your
+ * application's Makefile:
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ {.mk}
+ * USEMODULE += gnrc_netapi_mbox
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ * @}
+ *
+ * @defgroup    net_gnrc_netapi_callbacks   Callback extension
+ * @ingroup     net_gnrc_netapi
+ * @brief       Callback extension for @ref net_gnrc_netapi
+ * @{
+ * @details The submodule `gnrc_netapi_callbacks` provides an extension for
+ *          callbacks to run GNRC thread-less.
+ *
+ * To use, add the module `gnrc_netapi_callbacks` to the `USEMODULE` macro in
+ * your application's Makefile:
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ {.mk}
+ * USEMODULE += gnrc_netapi_callbacks
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ * @}
  * @author      Martine Lenders <mlenders@inf.fu-berlin.de>
  * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
  */
diff --git a/sys/include/net/gnrc/netreg.h b/sys/include/net/gnrc/netreg.h
index 0b7b48a86f30..e078a51d9c2d 100644
--- a/sys/include/net/gnrc/netreg.h
+++ b/sys/include/net/gnrc/netreg.h
@@ -27,10 +27,27 @@
 #include "net/gnrc/nettype.h"
 #include "net/gnrc/pkt.h"
 
+#ifdef MODULE_GNRC_NETAPI_MBOX
+#include "mbox.h"
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(MODULE_GNRC_NETAPI_CALLBACKS) || \
+    defined(DOXYGEN)
+typedef enum {
+    GNRC_NETREG_TYPE_DEFAULT = 0,
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(DOXYGEN)
+    GNRC_NETREG_TYPE_MBOX,
+#endif
+#if defined(MODULE_GNRC_NETAPI_CALLBACKS) || defined(DOXYGEN)
+    GNRC_NETREG_TYPE_CB,
+#endif
+} gnrc_netreg_type_t;
+#endif
+
 /**
  * @brief   Demux context value to get all packets of a certain type.
  *
@@ -47,7 +64,72 @@ extern "C" {
  *
  * @return  An initialized netreg entry
  */
-#define GNRC_NETREG_ENTRY_INIT_PID(demux_ctx, pid)  { NULL, demux_ctx, pid }
+#ifdef MODULE_GNRC_NETAPI_MBOX
+#define GNRC_NETREG_ENTRY_INIT_PID(demux_ctx, pid)  { NULL, demux_ctx, \
+                                                      GNRC_NETREG_TYPE_DEFAULT, \
+                                                      { pid } }
+#else
+#define GNRC_NETREG_ENTRY_INIT_PID(demux_ctx, pid)  { NULL, demux_ctx, { pid } }
+#endif
+
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(DOXYGEN)
+/**
+ * @brief   Initializes a netreg entry statically with mbox
+ *
+ * @param[in] demux_ctx The @ref gnrc_netreg_entry_t::demux_ctx "demux context"
+ *                      for the netreg entry
+ * @param[in] mbox      Target @ref core_mbox "mailbox" for the registry entry
+ *
+ * @note    Only available with @ref net_gnrc_netapi_mbox.
+ *
+ * @return  An initialized netreg entry
+ */
+#define GNRC_NETREG_ENTRY_INIT_MBOX(demux_ctx, mbox) { NULL, demux_ctx, \
+                                                       GNRC_NETREG_TYPE_MBOX, \
+                                                       { .mbox = mbox } }
+#endif
+
+#if defined(MODULE_GNRC_NETAPI_CALLBACKS) || defined(DOXYGEN)
+/**
+ * @brief   Initializes a netreg entry statically with callback
+ *
+ * @param[in] demux_ctx The @ref gnrc_netreg_entry_t::demux_ctx "demux context"
+ *                      for the netreg entry
+ * @param[in] cb        Target callback for the registry entry
+ *
+ * @note    Only available with @ref net_gnrc_netapi_callbacks.
+ *
+ * @return  An initialized netreg entry
+ */
+#define GNRC_NETREG_ENTRY_INIT_CB(demux_ctx, cbd)   { NULL, demux_ctx, \
+                                                      GNRC_NETREG_TYPE_CB, \
+                                                      { .cbd = cbd } }
+
+/**
+ * @brief   Packet handler callback for netreg entries with callback.
+ *
+ * @pre `cmd` $\in$ { @ref GNRC_NETAPI_MSG_TYPE_RCV, @ref GNRC_NETAPI_MSG_TYPE_SND }
+ *
+ * @note    Only available with @ref net_gnrc_netapi_callbacks.
+ *
+ * @param[in] cmd   @ref net_gnrc_netapi command type. Must be either
+ *                  @ref GNRC_NETAPI_MSG_TYPE_SND or
+ *                  @ref GNRC_NETAPI_MSG_TYPE_RCV
+ * @param[in] pkt   The packet to handle.
+ * @param[in] ctx   Application context.
+ */
+typedef void (*gnrc_netreg_entry_cb_t)(uint16_t cmd, gnrc_pktsnip_t *pkt,
+                                       void *ctx);
+
+/**
+ * @brief   Callback + Context descriptor
+ * @note    Only available with @ref net_gnrc_netapi_callbacks.
+ */
+typedef struct {
+    gnrc_netreg_entry_cb_t cb;  /**< the callback */
+    void *ctx;                  /**< application context for the callback */
+} gnrc_netreg_entry_cbd_t;
+#endif
 
 /**
  * @brief   Entry to the @ref net_gnrc_netreg
@@ -68,7 +150,36 @@ typedef struct gnrc_netreg_entry {
      *          ports in UDP/TCP, or similar.
      */
     uint32_t demux_ctx;
-    kernel_pid_t pid;       /**< The PID of the registering thread */
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(MODULE_GNRC_NETAPI_CALLBACKS) || \
+    defined(DOXYGEN)
+    /**
+     * @brief   Type of the registry entry
+     *
+     * @note    Only available with @ref net_gnrc_netapi_mbox or
+     *          @ref net_gnrc_netapi_callbacks.
+     */
+    gnrc_netreg_type_t type;
+#endif
+    union {
+        kernel_pid_t pid;       /**< The PID of the registering thread */
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(DOXYGEN)
+        /**
+         * @brief   Target @ref core_mbox "mailbox" for the registry entry
+         *
+         * @note    Only available with @ref net_gnrc_netapi_mbox.
+         */
+        mbox_t *mbox;
+#endif
+
+#if defined(MODULE_GNRC_NETAPI_CALLBACKS) || defined(DOXYGEN)
+        /**
+         * @brief   Target callback for the registry entry
+         *
+         * @note    Only available with @ref net_gnrc_netapi_callbacks.
+         */
+        gnrc_netreg_entry_cbd_t *cbd;
+#endif
+    } target;                   /**< Target for the registry entry */
 } gnrc_netreg_entry_t;
 
 /**
@@ -91,9 +202,56 @@ static inline void gnrc_netreg_entry_init_pid(gnrc_netreg_entry_t *entry,
 {
     entry->next = NULL;
     entry->demux_ctx = demux_ctx;
-    entry->pid = pid;
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(MODULE_GNRC_NETAPI_CALLBACKS)
+    entry->type = GNRC_NETREG_TYPE_DEFAULT;
+#endif
+    entry->target.pid = pid;
 }
 
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(DOXYGEN)
+/**
+ * @brief   Initializes a netreg entry dynamically with mbox
+ *
+ * @param[out] entry    A netreg entry
+ * @param[in] demux_ctx The @ref gnrc_netreg_entry_t::demux_ctx "demux context"
+ *                      for the netreg entry
+ * @param[in] mbox      Target @ref core_mbox "mailbox" for the registry entry
+ *
+ * @note    Only available with @ref net_gnrc_netapi_mbox.
+ */
+static inline void gnrc_netreg_entry_init_mbox(gnrc_netreg_entry_t *entry,
+                                               uint32_t demux_ctx,
+                                               mbox_t *mbox)
+{
+    entry->next = NULL;
+    entry->demux_ctx = demux_ctx;
+    entry->type = GNRC_NETREG_TYPE_MBOX;
+    entry->target.mbox = mbox;
+}
+#endif
+
+#if defined(MODULE_GNRC_NETAPI_CALLBACKS) || defined(DOXYGEN)
+/**
+ * @brief   Initializes a netreg entry dynamically with callback
+ *
+ * @param[out] entry    A netreg entry
+ * @param[in] demux_ctx The @ref gnrc_netreg_entry_t::demux_ctx "demux context"
+ *                      for the netreg entry
+ * @param[in] mbox      Target callback for the registry entry
+ *
+ * @note    Only available with @ref net_gnrc_netapi_callbacks.
+ */
+static inline void gnrc_netreg_entry_init_cb(gnrc_netreg_entry_t *entry,
+                                             uint32_t demux_ctx,
+                                             gnrc_netreg_entry_cbd_t *cbd)
+{
+    entry->next = NULL;
+    entry->demux_ctx = demux_ctx;
+    entry->type = GNRC_NETREG_TYPE_CB;
+    entry->target.cbd = cbd;
+}
+#endif
+
 /**
  * @brief   Registers a thread to the registry.
  *
diff --git a/sys/net/gnrc/conn/ip/gnrc_conn_ip.c b/sys/net/gnrc/conn/ip/gnrc_conn_ip.c
index b2311b7b2e09..d616f3b01375 100644
--- a/sys/net/gnrc/conn/ip/gnrc_conn_ip.c
+++ b/sys/net/gnrc/conn/ip/gnrc_conn_ip.c
@@ -52,7 +52,7 @@ int conn_ip_create(conn_ip_t *conn, const void *addr, size_t addr_len, int famil
 void conn_ip_close(conn_ip_t *conn)
 {
     assert(conn->l4_type == GNRC_NETTYPE_UNDEF);
-    if (conn->netreg_entry.pid != KERNEL_PID_UNDEF) {
+    if (conn->netreg_entry.target.pid != KERNEL_PID_UNDEF) {
         gnrc_netreg_unregister(conn->l3_type, &conn->netreg_entry);
     }
 }
diff --git a/sys/net/gnrc/conn/udp/gnrc_conn_udp.c b/sys/net/gnrc/conn/udp/gnrc_conn_udp.c
index fc18a950ced8..89ee02443bba 100644
--- a/sys/net/gnrc/conn/udp/gnrc_conn_udp.c
+++ b/sys/net/gnrc/conn/udp/gnrc_conn_udp.c
@@ -56,9 +56,9 @@ int conn_udp_create(conn_udp_t *conn, const void *addr, size_t addr_len,
 void conn_udp_close(conn_udp_t *conn)
 {
     assert(conn->l4_type == GNRC_NETTYPE_UDP);
-    if (conn->netreg_entry.pid != KERNEL_PID_UNDEF) {
+    if (conn->netreg_entry.target.pid != KERNEL_PID_UNDEF) {
         gnrc_netreg_unregister(GNRC_NETTYPE_UDP, &conn->netreg_entry);
-        conn->netreg_entry.pid = KERNEL_PID_UNDEF;
+        conn->netreg_entry.target.pid = KERNEL_PID_UNDEF;
     }
 }
 
diff --git a/sys/net/gnrc/netapi/gnrc_netapi.c b/sys/net/gnrc/netapi/gnrc_netapi.c
index a6294cbcabb8..d110ebf34af4 100644
--- a/sys/net/gnrc/netapi/gnrc_netapi.c
+++ b/sys/net/gnrc/netapi/gnrc_netapi.c
@@ -18,6 +18,7 @@
  * @}
  */
 
+#include "mbox.h"
 #include "msg.h"
 #include "net/gnrc/netreg.h"
 #include "net/gnrc/pktbuf.h"
@@ -74,6 +75,22 @@ static inline int _snd_rcv(kernel_pid_t pid, uint16_t type, gnrc_pktsnip_t *pkt)
     return ret;
 }
 
+#ifdef MODULE_GNRC_NETAPI_MBOX
+static inline int _snd_rcv_mbox(mbox_t *mbox, uint16_t type, gnrc_pktsnip_t *pkt)
+{
+    msg_t msg;
+    /* set the outgoing message's fields */
+    msg.type = type;
+    msg.content.ptr = (void *)pkt;
+    /* send message */
+    int ret = mbox_try_put(mbox, &msg);
+    if (ret < 1) {
+        DEBUG("gnrc_netapi: dropped message to %p (was full)\n", mbox);
+    }
+    return ret;
+}
+#endif
+
 int gnrc_netapi_dispatch(gnrc_nettype_t type, uint32_t demux_ctx,
                          uint16_t cmd, gnrc_pktsnip_t *pkt)
 {
@@ -85,10 +102,42 @@ int gnrc_netapi_dispatch(gnrc_nettype_t type, uint32_t demux_ctx,
         gnrc_pktbuf_hold(pkt, numof - 1);
 
         while (sendto) {
-            if (_snd_rcv(sendto->pid, cmd, pkt) < 1) {
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(MODULE_GNRC_NETAPI_CALLBACKS)
+            int release = 0;
+            switch (sendto->type) {
+                case GNRC_NETREG_TYPE_DEFAULT:
+                    if (_snd_rcv(sendto->target.pid, cmd, pkt) < 1) {
+                        /* unable to dispatch packet */
+                        release = 1;
+                    }
+                    break;
+#ifdef MODULE_GNRC_NETAPI_MBOX
+                case GNRC_NETREG_TYPE_MBOX:
+                    if (_snd_rcv_mbox(sendto->target.mbox, cmd, pkt) < 1) {
+                        /* unable to dispatch packet */
+                        release = 1;
+                    }
+                    break;
+#endif
+#ifdef MODULE_GNRC_NETAPI_CALLBACKS
+                case GNRC_NETREG_TYPE_CB:
+                    sendto->target.cbd->cb(cmd, pkt, sendto->target.cbd->ctx);
+                    break;
+#endif
+                default:
+                    /* unknown dispatch type */
+                    release = 1;
+                    break;
+            }
+            if (release) {
+                gnrc_pktbuf_release(pkt);
+            }
+#else
+            if (_snd_rcv(sendto->target.pid, cmd, pkt) < 1) {
                 /* unable to dispatch packet */
                 gnrc_pktbuf_release(pkt);
             }
+#endif
             sendto = gnrc_netreg_getnext(sendto);
         }
     }
diff --git a/sys/net/gnrc/netreg/gnrc_netreg.c b/sys/net/gnrc/netreg/gnrc_netreg.c
index 7effd16f120e..a01c557c7290 100644
--- a/sys/net/gnrc/netreg/gnrc_netreg.c
+++ b/sys/net/gnrc/netreg/gnrc_netreg.c
@@ -37,8 +37,16 @@ void gnrc_netreg_init(void)
 
 int gnrc_netreg_register(gnrc_nettype_t type, gnrc_netreg_entry_t *entry)
 {
+#if defined(MODULE_GNRC_NETAPI_MBOX) || defined(MODULE_GNRC_NETAPI_CALLBACKS)
+#ifdef DEVELHELP
     /* only threads with a message queue are allowed to register at gnrc */
-    assert(sched_threads[entry->pid]->msg_array);
+    assert((entry->type != GNRC_NETREG_TYPE_DEFAULT) ||
+           sched_threads[entry->target.pid]->msg_array);
+#endif
+#else
+    /* only threads with a message queue are allowed to register at gnrc */
+    assert(sched_threads[entry->target.pid]->msg_array);
+#endif
 
     if (_INVALID_TYPE(type)) {
         return -EINVAL;
diff --git a/sys/net/gnrc/routing/rpl/gnrc_rpl.c b/sys/net/gnrc/routing/rpl/gnrc_rpl.c
index df4e5ab89a7b..29fffd03b5be 100644
--- a/sys/net/gnrc/routing/rpl/gnrc_rpl.c
+++ b/sys/net/gnrc/routing/rpl/gnrc_rpl.c
@@ -68,7 +68,7 @@ kernel_pid_t gnrc_rpl_init(kernel_pid_t if_pid)
         }
 
         _me_reg.demux_ctx = ICMPV6_RPL_CTRL;
-        _me_reg.pid = gnrc_rpl_pid;
+        _me_reg.target.pid = gnrc_rpl_pid;
         /* register interest in all ICMPv6 packets */
         gnrc_netreg_register(GNRC_NETTYPE_ICMPV6, &_me_reg);
 
diff --git a/tests/slip/main.c b/tests/slip/main.c
index 6d7299ef9943..89fbaf88c0d4 100644
--- a/tests/slip/main.c
+++ b/tests/slip/main.c
@@ -36,7 +36,7 @@ int main(void)
     puts("SLIP test");
 
     /* register pktdump */
-    if (dump.pid <= KERNEL_PID_UNDEF) {
+    if (dump.target.pid <= KERNEL_PID_UNDEF) {
         puts("Error starting pktdump thread");
         return -1;
     }
diff --git a/tests/unittests/tests-netreg/tests-netreg.c b/tests/unittests/tests-netreg/tests-netreg.c
index d6b2d8a9a470..b56a68861f9f 100644
--- a/tests/unittests/tests-netreg/tests-netreg.c
+++ b/tests/unittests/tests-netreg/tests-netreg.c
@@ -45,7 +45,7 @@ static void test_netreg_register__success(void)
     TEST_ASSERT_EQUAL_INT(0, gnrc_netreg_register(GNRC_NETTYPE_TEST, &entries[0]));
     TEST_ASSERT_NOT_NULL((res = gnrc_netreg_lookup(GNRC_NETTYPE_TEST, TEST_UINT16)));
     TEST_ASSERT_EQUAL_INT(TEST_UINT16, res->demux_ctx);
-    TEST_ASSERT_EQUAL_INT(TEST_UINT8, res->pid);
+    TEST_ASSERT_EQUAL_INT(TEST_UINT8, res->target.pid);
     TEST_ASSERT_NULL((gnrc_netreg_getnext(res)));
 }
 
@@ -66,7 +66,7 @@ void test_netreg_unregister__success2(void)
     gnrc_netreg_unregister(GNRC_NETTYPE_TEST, &entries[0]);
     TEST_ASSERT_NOT_NULL((res = gnrc_netreg_lookup(GNRC_NETTYPE_TEST, TEST_UINT16)));
     TEST_ASSERT_EQUAL_INT(TEST_UINT16, res->demux_ctx);
-    TEST_ASSERT_EQUAL_INT(TEST_UINT8 + 1, res->pid);
+    TEST_ASSERT_EQUAL_INT(TEST_UINT8 + 1, res->target.pid);
     gnrc_netreg_unregister(GNRC_NETTYPE_TEST, &entries[1]);
     TEST_ASSERT_NULL(gnrc_netreg_lookup(GNRC_NETTYPE_TEST, TEST_UINT16));
 }
@@ -80,7 +80,7 @@ void test_netreg_unregister__success3(void)
     gnrc_netreg_unregister(GNRC_NETTYPE_TEST, &entries[1]);
     TEST_ASSERT_NOT_NULL((res = gnrc_netreg_lookup(GNRC_NETTYPE_TEST, TEST_UINT16)));
     TEST_ASSERT_EQUAL_INT(TEST_UINT16, res->demux_ctx);
-    TEST_ASSERT_EQUAL_INT(TEST_UINT8, res->pid);
+    TEST_ASSERT_EQUAL_INT(TEST_UINT8, res->target.pid);
     gnrc_netreg_unregister(GNRC_NETTYPE_TEST, &entries[0]);
     TEST_ASSERT_NULL(gnrc_netreg_lookup(GNRC_NETTYPE_TEST, TEST_UINT16));
 }