A9

A9, A.9, A09, A 9 or A-9 may refer to

Science

ATC code A09 Digestives, including enzymes, a subgroup of the Anatomical Therapeutic Chemical Classification System
Biolimus A9, an immunosuppressant
British NVC community A9, the Potamogeton natans community, one of the aquatic communities of the British National Vegetation Classification
HLA-A9, a broad antigen serogroup of Human MHC HLA-A
Subfamily A9, a Rhodopsin-like receptors subfamily

Breda A.9, a 1928 Italian biplane trainer aircraft
CallAir A-9 Quail, an agricultural aircraft
Georgian Airways's IATA code
Lockheed A-9, a ground attack aircraft based on the Lockheed YP-24 fighter prototype
Northrop YA-9, a ground-attack aircraft that competed with the Fairchild Republic A-10 Thunderbolt II

A9 (classification), an amputee sport classification
A9 road, in several countries, see List of A9 roads
A9, an international ISO 216 paper size standard (37×52 mm)
A-9 Vigilance, a fictional starfighter from the Star Wars universe
Arrows A9, a 1986 British racing car
HMNZS Manawanui (A09), a 1988 diving support vessel for the Royal New Zealand Navy
HMS A9, an A-class submarine of the Royal Navy
Réti Opening or A09, a chess opening
A9 TV, a Turkish television station