Assistant Secretary of State for International Security and Nonproliferation

{{Use American English|date = March 2019}}

{{Short description|U.S. government position}}

{{Use mdy dates|date = March 2019}}

{{Infobox Political post

| post = United States
Assistant Secretary of State
for International Security and Nonproliferation

| body =

| insignia = U.S. Department of State official seal.svg

| insigniasize = 120px

| insigniacaption = Seal of the United States Department of State

| imagesize = 200px

| image =

| incumbent = Paul Watzlavickhttps://www.state.gov/biographies/paul-watzlavick/

| acting = yes

| incumbentsince = March 7, 2025

| style =

| residence =

| termlength =

| reports_to = Under Secretary of State for Arms Control and International Security Affairs

| nominator = President of the United States

| formation = 2005

| inaugural = Stephen Rademaker (acting)

| website = {{url|www.state.gov/t/isn/index.htm}}

| flag = Flag of the United States Assistant Secretary of State.svg

| flagcaption = Flag of an Assistant Secretary of State

}}

The Assistant Secretary of State for International Security and Nonproliferation is the head of the Bureau of International Security and Nonproliferation, which is responsible for managing the nonproliferation, counter-proliferation functions of the United States Department of State. The position was created on September 13, 2005, when the Bureau of Arms Control and the Bureau of Nonproliferation were merged. The Assistant Secretary of State for International Security and Nonproliferation reports to the Under Secretary of State for Arms Control and International Security Affairs.

Stephen Rademaker was the first Acting Assistant Secretary of State for International Security and Nonproliferation. He had been the Assistant Secretary for the Bureau of Arms Control, and in February 2005 he was named the head of the Bureau for Nonproliferation pending the two bureaus' merger.