A66, A 66 or A-66 may refer to:
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A66 State Route (Australia)
Riddoch Highway is a rural highway in south-eastern South Australia, designated as route A66 between Keith and Mount Gambier, with the remainder between Mount Gambier and Port MacDonnell designated as route B66. It is named after John Riddoch, t ...
, a road in South Australia connecting Keith and Port MacDonnell
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Autopista 66 (Cuba), motorway connecting the Autopista Nacional with Sancti Spiritus
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A66 road (England), a road connecting Middlesbrough and Penrith/Workington
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A66 motorway (France), a road connecting Villefranche-de-Lauragais and Pamiers
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A66 motorway (Germany), a road connecting the Taunus and Fulda
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A66 motorway (Spain), a road connecting Gijón and Seville
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Benoni Defense, in the Encyclopaedia of Chess Openings
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HLA-A66, an HLA-A serotype
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