A1

A1, A-1 or A.1.may refer to:


 * A1, the highest category of Qualified Flying Instructor in the Central Flying School of the UK Royal Air Force
 * A-1 Skyraider, a United States military attack aircraft
 * A-1 flying jacket, the predecessor of the A-2 flying jacket
 * Company A-1, an outfit in the Texas A&M Corps of Cadets
 * Svea Artillery Regiment, a Swedish Army regiment
 * A-1 (code) was the designation for a code used by the United States Navy during World War I
 * A1, a designation of military staff in the continental staff system
 * A-1, a grade of Republic of China List of orders, decorations and medals of the Republic of China
 * Forces A1, a naval force in the Battle of Crete, see Crete order of battle
 * A-1, Brazilian Air Forces designation for the AMX International AMX aircraft
 * Kampfgeschwader 53, from its historic Geschwaderkennung code with the Luftwaffe in World War II

Aircraft

 * A-1 Skyraider

Seacraft

 * Boats
 * A-1 lifeboat
 * USS A-1, the name of multiple US Navy ships
 * ARA Comandante General Irigoyen (A-1), an Argentine Navy auxiliary ship
 * Submarines
 * HMS A1, a British A class submarine of the Royal Navy
 * A1 type submarine, a type of Japanese Navy submarine
 * HNoMS Kobben (A-1), a Royal Norwegian Navy submarine