The New Testament contains 21 epistles — letters written to early Christian churches and individuals. Traditionally, 13 are attributed to the Apostle Paul; the remaining 8 include the anonymous Epistle to the Hebrews and the "general" or "catholic" epistles.
Pauline epistles (13, traditionally attributed to Paul)
Romans, 1 Corinthians, 2 Corinthians, Galatians, Ephesians, Philippians, Colossians, 1 Thessalonians, 2 Thessalonians, 1 Timothy, 2 Timothy, Titus, Philemon.
General epistles (8)
Hebrews, James, 1 Peter, 2 Peter, 1 John, 2 John, 3 John, Jude. Hebrews is anonymous — no author is named in the text.