A66, A 66 or A-66 may refer to:
Roads A66 State Route (Australia), a road in South Australia connecting Keith and Port MacDonnell Autopista 66 (Cuba), motorway connecting the Autopista Nacional with Sancti Spiritus A66 road, a road connecting Middlesbrough and Penrith/Workington in England A66 motorway (France), a road connecting Villefranche-de-Lauragais and Pamiers A66 motorway (Germany), a road connecting the Taunus and Fulda A66 motorway (Spain), a road connecting Gijón and Seville
Other uses Benoni Defense, in the Encyclopaedia of Chess Openings HLA-A66, an HLA-A serotype