AR2 may refer to:
AR2 (train), European railbus Arkhangelsky Ar-2, Soviet dive bomber Arkansas's 2nd congressional district Arkansas Highway 2 Dorand AR2, a French two-seater aircraft of World War I, also converted to a two-casualty ambulance version Ar2, the chemical formula for diargon
See also SAR (IPCC), the IPCC Second Assessment Report (aka AR2)