Clement of Alexandria (c. 150–200) was the head of the catechetical school in the church at Alexandria. His most famous pupil was Origen
Besides, there are writings of certain brethren older than the times of Victor, which they wrote against the pagans in defense of the truth and against the heresies of their day. I mean Justin, Miltiades, Tatian, Clement, and many others. In all their writings, divinity is ascribed to Christ. Eusebius, quoting Caius (c. 215, W), 5.601
I have sent . . . this letter by the hand of the blessed presbyter Clement, a man virtuous and well tried, whom you already know. [This may or may not be a reference to Clement of Alexandria.] Alexander of Cappadocia (c. 250, E), 6.154
We are well acquainted with those blessed fathers who have trodden the course before, and to whom we too will soon go: namely, Pantaenus, the truly blessed man, my master; and also the holy Clement, who was once my master and my benefactor. Alexander of Cappadocia (c. 250, E), 6.154
Our predecessors, men most learned in the books of the Hebrews and Greeks (I refer to Isidore, Jerome, and Clement), . . . come harmoniously to one and the same most exact determination of Easter. Anatolius (c. 270, E), 6.146.