AT-3 may be:
*
AT III, a protein in the coagulation system that is activated by Heparin
*
AT-3 (jet trainer)
The AIDC AT-3 Tzu Chung (; "Self Reliance") is an advanced jet trainer operated by the Republic of China Air Force (ROCAF). A total of sixty-two aircraft were manufactured by the Aerospace Industrial Development Corporation of Taiwan in colla ...
of the Republic of China Air Force (Taiwan)
*
AT-3 plane, Very Light Aircraft
*
AT-3 Sagger
The 9M14 Malyutka (russian: Малютка, links=no; "Little one", NATO reporting name: AT-3 Sagger) is a manual command to line of sight (MCLOS) wire-guided anti-tank guided missile (ATGM) system developed in the Soviet Union. It was the f ...
, Soviet anti-tank missile
* AT-3 (
MATH-MATIC) compiler for UNIVAC mainframe computers
* .at3, extension for audio files compressed with Sony's
ATRAC3 algorithm
* ''
Ar tonelico Qoga: Knell of Ar Ciel'', a role-playing game for the PlayStation 3
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