Paul's letter to the Galatians was addressed to a group of churches in Galatia, a region of present day Turkey. Paul had preached the gospel in these churches. He wrote to counter those who taught that Christians must be circumcised in order to be accepted by God. Paul began with a defense of his apostolic authority, then made it clear that all believers, Jew and Gentile alike, enjoy complete salvation in Christ. In chapters 5-6 Paul showed how the gospel of grace leads to true freedom and godly living. Perhaps the central message of Galatians is "a person is not justified by works of the law but through faith in Jesus Christ". Paul wrote this letter sometime between A.D. 48 and 55.
From ESV Bible, Introduction to Galatians