diff --git a/targets/TARGET_NUVOTON/TARGET_M451/reset_reason.c b/targets/TARGET_NUVOTON/TARGET_M451/reset_reason.c
new file mode 100644
index 0000000000..91c29b6512
--- /dev/null
+++ b/targets/TARGET_NUVOTON/TARGET_M451/reset_reason.c
@@ -0,0 +1,106 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2017-2018 Nuvoton
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "reset_reason_api.h"
+
+#if DEVICE_RESET_REASON
+
+#include "cmsis.h"
+
+/* All reset source flags */
+#define SYS_RSTSTS_ALLRF_Msk    \
+    (SYS_RSTSTS_PORF_Msk |      \
+    SYS_RSTSTS_PINRF_Msk |      \
+    SYS_RSTSTS_WDTRF_Msk |      \
+    SYS_RSTSTS_LVRF_Msk |       \
+    SYS_RSTSTS_BODRF_Msk |      \
+    SYS_RSTSTS_SYSRF_Msk |      \
+    SYS_RSTSTS_CPURF_Msk |      \
+    SYS_RSTSTS_CPULKRF_Msk)
+
+reset_reason_t hal_reset_reason_get(void)
+{
+    uint32_t reset_reason_raw = hal_reset_reason_get_raw();
+    reset_reason_t reset_reason_cast;
+    uint32_t reset_reason_count = 0;
+
+    if (SYS_IS_POR_RST()) {
+        reset_reason_cast = RESET_REASON_POWER_ON;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_RSTPIN_RST()) {
+        reset_reason_cast = RESET_REASON_PIN_RESET;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_WDT_RST()) {
+        reset_reason_cast = RESET_REASON_WATCHDOG;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_LVR_RST()) {
+        reset_reason_cast = RESET_REASON_PLATFORM;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_BOD_RST()) {
+        reset_reason_cast = RESET_REASON_BROWN_OUT;
+        reset_reason_count ++;
+    }
+
+    /* This MCU supports MKROM and we need to take care of bootloader/SYSRESETREQ flow. */
+    if (SYS_IS_SYSTEM_RST()) {
+        if (reset_reason_raw & (SYS_RSTSTS_ALLRF_Msk & ~SYS_RSTSTS_SYSRF_Msk)) {
+            /* We may boot from bootloader which would reset to go to LDROM/APROM at its end
+             * through writing 1 to SYSRESETREQ bit. If there are other reset reasons, we think
+             * it is just the case and ignore the reset reason with SYSRESETREQ. */
+        } else {
+            reset_reason_cast = RESET_REASON_SOFTWARE;
+            reset_reason_count ++;
+        }
+    }
+
+    if (SYS_IS_CPU_RST()) {
+        reset_reason_cast = RESET_REASON_PLATFORM;
+        reset_reason_count ++;
+    }
+
+    if (reset_reason_raw & SYS_RSTSTS_CPULKRF_Msk) {
+        reset_reason_cast = RESET_REASON_LOCKUP;
+        reset_reason_count ++;
+    }
+
+    if (reset_reason_count == 0) {
+        reset_reason_cast = RESET_REASON_UNKNOWN;
+    } else if (reset_reason_count >= 2) {
+        reset_reason_cast = RESET_REASON_MULTIPLE;
+    }
+
+    return reset_reason_cast;
+}
+
+uint32_t hal_reset_reason_get_raw(void)
+{
+    return (SYS->RSTSTS & SYS_RSTSTS_ALLRF_Msk);
+}
+
+void hal_reset_reason_clear(void)
+{
+    SYS_CLEAR_RST_SOURCE(SYS->RSTSTS);
+}
+
+#endif
diff --git a/targets/TARGET_NUVOTON/TARGET_M480/reset_reason.c b/targets/TARGET_NUVOTON/TARGET_M480/reset_reason.c
new file mode 100644
index 0000000000..91c29b6512
--- /dev/null
+++ b/targets/TARGET_NUVOTON/TARGET_M480/reset_reason.c
@@ -0,0 +1,106 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2017-2018 Nuvoton
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "reset_reason_api.h"
+
+#if DEVICE_RESET_REASON
+
+#include "cmsis.h"
+
+/* All reset source flags */
+#define SYS_RSTSTS_ALLRF_Msk    \
+    (SYS_RSTSTS_PORF_Msk |      \
+    SYS_RSTSTS_PINRF_Msk |      \
+    SYS_RSTSTS_WDTRF_Msk |      \
+    SYS_RSTSTS_LVRF_Msk |       \
+    SYS_RSTSTS_BODRF_Msk |      \
+    SYS_RSTSTS_SYSRF_Msk |      \
+    SYS_RSTSTS_CPURF_Msk |      \
+    SYS_RSTSTS_CPULKRF_Msk)
+
+reset_reason_t hal_reset_reason_get(void)
+{
+    uint32_t reset_reason_raw = hal_reset_reason_get_raw();
+    reset_reason_t reset_reason_cast;
+    uint32_t reset_reason_count = 0;
+
+    if (SYS_IS_POR_RST()) {
+        reset_reason_cast = RESET_REASON_POWER_ON;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_RSTPIN_RST()) {
+        reset_reason_cast = RESET_REASON_PIN_RESET;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_WDT_RST()) {
+        reset_reason_cast = RESET_REASON_WATCHDOG;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_LVR_RST()) {
+        reset_reason_cast = RESET_REASON_PLATFORM;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_BOD_RST()) {
+        reset_reason_cast = RESET_REASON_BROWN_OUT;
+        reset_reason_count ++;
+    }
+
+    /* This MCU supports MKROM and we need to take care of bootloader/SYSRESETREQ flow. */
+    if (SYS_IS_SYSTEM_RST()) {
+        if (reset_reason_raw & (SYS_RSTSTS_ALLRF_Msk & ~SYS_RSTSTS_SYSRF_Msk)) {
+            /* We may boot from bootloader which would reset to go to LDROM/APROM at its end
+             * through writing 1 to SYSRESETREQ bit. If there are other reset reasons, we think
+             * it is just the case and ignore the reset reason with SYSRESETREQ. */
+        } else {
+            reset_reason_cast = RESET_REASON_SOFTWARE;
+            reset_reason_count ++;
+        }
+    }
+
+    if (SYS_IS_CPU_RST()) {
+        reset_reason_cast = RESET_REASON_PLATFORM;
+        reset_reason_count ++;
+    }
+
+    if (reset_reason_raw & SYS_RSTSTS_CPULKRF_Msk) {
+        reset_reason_cast = RESET_REASON_LOCKUP;
+        reset_reason_count ++;
+    }
+
+    if (reset_reason_count == 0) {
+        reset_reason_cast = RESET_REASON_UNKNOWN;
+    } else if (reset_reason_count >= 2) {
+        reset_reason_cast = RESET_REASON_MULTIPLE;
+    }
+
+    return reset_reason_cast;
+}
+
+uint32_t hal_reset_reason_get_raw(void)
+{
+    return (SYS->RSTSTS & SYS_RSTSTS_ALLRF_Msk);
+}
+
+void hal_reset_reason_clear(void)
+{
+    SYS_CLEAR_RST_SOURCE(SYS->RSTSTS);
+}
+
+#endif
diff --git a/targets/TARGET_NUVOTON/TARGET_NANO100/reset_reason.c b/targets/TARGET_NUVOTON/TARGET_NANO100/reset_reason.c
new file mode 100644
index 0000000000..a2ea29c464
--- /dev/null
+++ b/targets/TARGET_NUVOTON/TARGET_NANO100/reset_reason.c
@@ -0,0 +1,87 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2017-2018 Nuvoton
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "reset_reason_api.h"
+
+#if DEVICE_RESET_REASON
+
+#include "cmsis.h"
+
+/* All reset source flags */
+#define SYS_RST_SRC_ALL_Msk         \
+    (SYS_RST_SRC_RSTS_POR_Msk |     \
+    SYS_RST_SRC_RSTS_PAD_Msk |      \
+    SYS_RST_SRC_RSTS_WDT_Msk |      \
+    SYS_RST_SRC_RSTS_BOD_Msk |      \
+    SYS_RST_SRC_RSTS_SYS_Msk |      \
+    SYS_RST_SRC_RSTS_CPU_Msk)
+
+reset_reason_t hal_reset_reason_get(void)
+{
+    reset_reason_t reset_reason_cast;
+    uint32_t reset_reason_count = 0;
+
+    if (SYS_IS_POR_RST()) {
+        reset_reason_cast = RESET_REASON_POWER_ON;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_RSTPIN_RST()) {
+        reset_reason_cast = RESET_REASON_PIN_RESET;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_WDT_RST()) {
+        reset_reason_cast = RESET_REASON_WATCHDOG;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_BOD_RST()) {
+        reset_reason_cast = RESET_REASON_BROWN_OUT;
+        reset_reason_count ++;
+    }
+
+    /* This MCU doesn't support MKROM and we needn't take care of bootloader/SYSRESETREQ flow. */
+    if (SYS_IS_SYSTEM_RST()) {
+        reset_reason_cast = RESET_REASON_SOFTWARE;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_CPU_RST()) {
+        reset_reason_cast = RESET_REASON_PLATFORM;
+        reset_reason_count ++;
+    }
+
+    if (reset_reason_count == 0) {
+        reset_reason_cast = RESET_REASON_UNKNOWN;
+    } else if (reset_reason_count >= 2) {
+        reset_reason_cast = RESET_REASON_MULTIPLE;
+    }
+
+    return reset_reason_cast;
+}
+
+uint32_t hal_reset_reason_get_raw(void)
+{
+    return (SYS->RST_SRC & SYS_RST_SRC_ALL_Msk);
+}
+
+void hal_reset_reason_clear(void)
+{
+    SYS_CLEAR_RST_SOURCE(SYS->RST_SRC);
+}
+
+#endif
diff --git a/targets/TARGET_NUVOTON/TARGET_NUC472/reset_reason.c b/targets/TARGET_NUVOTON/TARGET_NUC472/reset_reason.c
new file mode 100644
index 0000000000..2f8f5bc515
--- /dev/null
+++ b/targets/TARGET_NUVOTON/TARGET_NUC472/reset_reason.c
@@ -0,0 +1,93 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2017-2018 Nuvoton
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "reset_reason_api.h"
+
+#if DEVICE_RESET_REASON
+
+#include "cmsis.h"
+
+/* All reset source flags */
+#define SYS_RSTSTS_ALLRF_Msk    \
+    (SYS_RSTSTS_PORF_Msk |      \
+    SYS_RSTSTS_PINRF_Msk |      \
+    SYS_RSTSTS_WDTRF_Msk |      \
+    SYS_RSTSTS_LVRF_Msk |       \
+    SYS_RSTSTS_BODRF_Msk |      \
+    SYS_RSTSTS_SYSRF_Msk |      \
+    SYS_RSTSTS_CPURF_Msk)
+
+reset_reason_t hal_reset_reason_get(void)
+{
+    reset_reason_t reset_reason_cast;
+    uint32_t reset_reason_count = 0;
+
+    if (SYS_IS_POR_RST()) {
+        reset_reason_cast = RESET_REASON_POWER_ON;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_RSTPIN_RST()) {
+        reset_reason_cast = RESET_REASON_PIN_RESET;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_WDT_RST()) {
+        reset_reason_cast = RESET_REASON_WATCHDOG;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_LVR_RST()) {
+        reset_reason_cast = RESET_REASON_PLATFORM;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_BOD_RST()) {
+        reset_reason_cast = RESET_REASON_BROWN_OUT;
+        reset_reason_count ++;
+    }
+
+    /* This MCU doesn't support MKROM and we needn't take care of bootloader/SYSRESETREQ flow. */
+    if (SYS_IS_SYSTEM_RST()) {
+        reset_reason_cast = RESET_REASON_SOFTWARE;
+        reset_reason_count ++;
+    }
+
+    if (SYS_IS_CPU_RST()) {
+        reset_reason_cast = RESET_REASON_PLATFORM;
+        reset_reason_count ++;
+    }
+
+    if (reset_reason_count == 0) {
+        reset_reason_cast = RESET_REASON_UNKNOWN;
+    } else if (reset_reason_count >= 2) {
+        reset_reason_cast = RESET_REASON_MULTIPLE;
+    }
+
+    return reset_reason_cast;
+}
+
+uint32_t hal_reset_reason_get_raw(void)
+{
+    return (SYS->RSTSTS & SYS_RSTSTS_ALLRF_Msk);
+}
+
+void hal_reset_reason_clear(void)
+{
+    SYS_CLEAR_RST_SOURCE(SYS->RSTSTS);
+}
+
+#endif
diff --git a/targets/targets.json b/targets/targets.json
index e93f8546d2..803ed21a50 100644
--- a/targets/targets.json
+++ b/targets/targets.json
@@ -6776,6 +6776,7 @@
             "PORTINOUT",
             "PORTOUT",
             "PWMOUT",
+            "RESET_REASON",
             "SERIAL",
             "SERIAL_ASYNCH",
             "SERIAL_FC",
@@ -6878,6 +6879,7 @@
             "PORTINOUT",
             "PORTOUT",
             "PWMOUT",
+            "RESET_REASON",
             "SERIAL",
             "SERIAL_ASYNCH",
             "SERIAL_FC",
@@ -7029,6 +7031,7 @@
             "PORTINOUT",
             "PORTOUT",
             "PWMOUT",
+            "RESET_REASON",
             "SERIAL",
             "SERIAL_ASYNCH",
             "SERIAL_FC",
@@ -7133,6 +7136,7 @@
             "PORTINOUT",
             "PORTOUT",
             "PWMOUT",
+            "RESET_REASON",
             "SERIAL",
             "SERIAL_ASYNCH",
             "SERIAL_FC",