Smith's Bible Dictionary

Achaia (trouble) signifies in the New Testament a Roman province which included the whole of the Peloponnesus and the greater part of Hellas proper, with the adjacent islands. This province, with that of Macedonia, comprehended the while of Greece; hence Achaia and Macedonia are frequently mentioned together in the New Testament to indicate all Greece. (Acts 18:12; Acts 19:21; Romans 15:2; Romans 16:5; 1 Corinthians 16:15; 2 Corinthians 7:5; 2 Corinthians 9:2; 2 Corinthians 11:10; 1 Thessalonians 1:7; 1 Thessalonians 1:8) In the time of the emperor Claudius it was governed by a proconsul, translated in the Authorized Version "deputy," of Achaia. (Acts 18:12)