Achaia, also spelled Achaea, was a Roman province south of Macedonia and consisted of the southern part of what we call “Greece” today. Achaia was originally the name for a narrow strip of land on the northwest side of the Peloponnesus peninsula. Later, the meaning of Achaia was expanded to include Attica, Boeotia, Euboea, the Cyclades, and Athens. The Roman capital of Achaia was Corinth, located on the southern end of the isthmus connecting the Peloponnesus with mainland Greece. Sometimes in the Bible, Achaia is called “Greece,” or is mentioned together with Macedonia to indicate all of modern-day Greece (e.g., Acts 19:21; Romans 16:5; 1 Corinthians 16:15; 2 Corinthians 11:10; 1 Thessalonians 1:7–8).
Paul traveled through Achaia on two of his missionary journeys. On his second journey, he stayed in Corinth for a year and a half to teach the new believers there (Acts 18:11). A man named Stephanas, along with his household, was the first convert to Christianity in Achaia (1 Corinthians 16:15). Gallio was proconsul, or governor, of Achaia during Paul’s stay in Corinth, around AD 51—52 (Acts 18:12). It was in Corinth that Paul met Aquila and Priscilla (Acts 18:2), supported himself through tent-making, and became the object of an attack by the unbelieving Jews (verses 12–13).
Paul spent many of his ministry years in or around the cities of Achaia, and he mentions the region in his letters to the churches in Thessalonica, Rome, and Corinth. During his brief stay in Athens, he spoke at the Areopagus to the philosophers gathered there (Acts 17:16–34). The evangelist Apollos also ministered in Achaia (Acts 19:1).
On his third missionary journey, Paul spent about three months in Achaia. From there, he had planned to sail to Syria, but just before he was to set sail, he discovered a plot against his life, and “he decided to go back through Macedonia” (Acts 20:3).