Justin Martyr was a Christian philosopher and writer in the mid-second century CE, during the Roman Empire. He was born to a non-Christian family in the city of Flavia Neapolis in Samaria. According to his own account, he studied various schools of Greek philosophy before converting to Christianity after a discussion with an old man who pointed him to the Hebrew prophets. After his conversion, he taught Christian philosophy, first in Ephesus and later in Rome, where he established a school. He was arrested after a dispute with a philosopher, tried before the Roman prefect, and executed for refusing to worship the Roman gods, which earned him the title "Martyr."

His major surviving works are defenses of Christian belief written for a Roman audience. The First Apology is addressed to the emperor, arguing that Christians are not criminals and that their faith is rational. The Second Apology is a shorter follow-up addressed to the Roman Senate. His Dialogue with Trypho records a lengthy debate with a Jewish scholar about the interpretation of scripture and the identity of Jesus. A fourth work, On the Resurrection, survives in fragments, though some scholars question its authenticity.

Justin Martyr is historically significant as the first major Christian "apologist" who systematically defended the faith to imperial authorities. According to modern scholars, his most important contribution was his use of Greek philosophy, especially the concept of the Logos (the "Word"), to explain Christian doctrine. He argued that figures like the Greek philosopher Socrates had partial access to the same divine truth that was fully revealed in Jesus Christ. This provided an early framework for synthesizing Christian belief with classical thought. His writings also offer invaluable descriptions of early Christian rituals, such as baptism and communion, making him a crucial source for understanding second-century Christianity.