CA3

CA3 may refer to:
 * Carbonic anhydrase III, muscle specific, a human gene
 * Cornu Ammonis region 3, one of the hippocampal subfields
 * United States Court of Appeals for the Third Circuit

CA-3 may refer to:
 * Buhl-Verville CA-3 Airster
 * Buhl CA-3 Airsedan
 * CAC CA-3 Wirraway
 * California's 3rd congressional district
 * California State Route 3

Ca.3 may refer to :
 * Caproni Ca.3, an Italian heavy bomber of World War I and the post-war era