A9

A9, A.9, A09, A 9 or A-9 can refer to
* A9, an international ISO 216 paper size standard (37×52 mm)
* A9, the designation for air force headquarters staff concerned with Civil-Military Co-operation
* A9.com, a website and search engine by Amazon.com
* A9 Cruiser Mk I, a British tank
* A9 rocket, a German rocket design in World War II
* A-9 Vigilance, a fictional starfighter from the Star Wars universe
* ATC code A09, a division of the Anatomical Therapeutic Chemical Classification System
* Breda A.9, a 1928 Italian biplane trainer aircraft
* British NVC community A9, the "Potamogeton natans" community, one of the aquatic communities of the British National Vegetation Classification
* CallAir A-9 Quail, an agricultural aircraft
* Gibson A-9 mandolin, a mandolin produced by Gibson corporation
* HLA-A9, a broad antigen serogroup of Human MHC HLA-A
* HMNZS Manawanui (A09), a 1988 diving support vessel for the Royal New Zealand Navy
* HMS "A9", an A-class submarine of the Royal Navy
* Lockheed A-9, a ground attack aircraft based on the Lockheed YP-24 fighter prototype

and also
* %A9, the Url Encoded version of the Copyright symbol (©)
* Alice Nine, a Japanese rock band
* Georgian Airways IATA code
* Grumman OA-9 "Goose" amphibious aircraft in USAAC service (redesignation of the G-21)
* Northrop YA-9, a prototype attack aircraft developed for the United States Air Force
* A 9, a Swedish regiment, according to the list of Swedish artillery regiments
* A09, Réti Opening code in the Encyclopaedia of Chess Openings

A9 Roads

* A9 autoroute, a French motorway
* A9 motorway (Cyprus)
* A9 motorway (Netherlands), a motorway in the Netherlands from Diemen to Alkmaar
* A9 road (Scotland), connecting Edinburgh to Thurso
* A9 road (Zimbabwe), a road in Zimbabwe
* Bundesautobahn 9 ("Autobahn 9"), a highway in Germany
* Autopista A9, a Spanish motorway
* Autostrada A9 (Italy)
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* A009, National Route A009 (Argentina)
* a national road in Latvia