Quintus Septimius Florens Tertullianus, anglicised as Tertullian (c. 160 – c. 225 CE), is a prolific early Christian author from Carthage in the Roman province of Africa.

He is the first Christian author to produce an extensive corpus of Latin Christian literature.

He also is a notable early Christian apologist and a polemicist against heresy.

Though conservative, he does originate and advance new theology to the early Church.

He is perhaps most famous for being the oldest extant Latin writer to use the term Trinity (Latin trinitas), and giving the oldest extant formal exposition of a Trinitarian theology.

[ Other Latin formulations that first appear in his work are "three Persons, one Substance" as the Latin "tres Personae, una Substantia" (itself from the Koine Greek "treis Hypostases, Homoousios").

He writes his trinitarian formula after becoming a Montanist; his ideas ae at first rejected as heresy by the church at large, but later accepted as Christian orthodoxy.