1st Regiment

The 1st Regiment or 1st Infantry Regiment may refer to any of a large number of military units:

Australia

 * 1st Infantry Regiment

France

 * 1st Marine Infantry Regiment (1er Régiment d'Infanterie de Marine, 1RIMa)
 * 1st Line Infantry Regiment (1er régiment d'infanterie de ligne, 1er RI)

Germany

 * 1. Infanterie-Regiment

New Zealand
In New Zealand service:
 * 1st (Canterbury) Regiment

Philippines

 * 1st Infantry Regiment (Philippine Commonwealth), The operations of the Filipino soldiers of the 1st Infantry Regiment of the Commonwealth Army of the Philippines from 1935 to 1946.
 * 1st Infantry Regiment (USAFIP-NL), The operations of the Filipino soldiers of the 1st Infantry Regiment of the United States Armed Forces in the Philippines - Northern Luzon or USAFIP-NL in the parts of the Philippine Commonwealth Army from 1944 to 1945.
 * 1st Infantry Regiment (Philippine Commonwealth), The operations of the Filipino soldiers of the 1st Infantry Regiment of the Philippine Constabulary from 1941 to 1942 and 1944 to 1946 under the U.S. military command and the military establishment and stationed in Northern Luzon, Philippines.

South Africa

 * Durban Light Infantry, formerly 1st Infantry (Durban Light Infantry)

United Kingdom

 * The Royal Scots, formerly the 1st (Royal) Regiment of Foot
 * Grenadier Guards, formerly the 1st Regiment of Foot Guards

United States of America

 * 1st Infantry Regiment (United States)
 * 1st Marine Regiment (United States)
 * 1st Regiment Massachusetts Volunteer Infantry (American Civil War)

Yugoslavia

 * 1st Fighter Regiment
 * 1st Yugoslav Fighter Regiment
 * 1st Transport Aviation Regiment
 * 1st Training Aviation Regiment
 * 1st Air Reconnaissance Regiment

Miscellaneous
It is also the name of an album by The Alchemist. For that, see 1st Infantry (album)