Pieter Cornelis (Piet) Mondrian Sr. was a Dutch teacher and lithographer and father of the famous painter Piet Mondrian.

He was a son of Willem Frederik Mondrian, a hairdresser, perfumer and wigmaker in The Hague. When his father died in 1878, his brother Frits took over his business. Pieter Cornelis married Johanna Christina de Kok (1839-1909) in The Hague on May 12, 1869.

He became a teacher in Amersfoort and headmaster of a newly established elementary school of the Christian National Education. They settled at Kortegracht 11, a double residence that also housed the school. Mondrian was an active member of the Anti-Revolutionary Party and supported Abraham Kuyper in his school struggle. Mondrian was thus a strict and conservative believer but, unlike his eldest son, would later not join Kuyper's Reformed Church.

In April 1880, at Kuyper's intercession, Mondrian became principal of an elementary school for Christian National Education in Winterswijk and settled there at Zonnebrink 4. His children were also among his pupils. Here he helped his son, Piet Mondrian, obtain the certificate of L.O. hand drawing for primary classes. He liked to see his eldest son succeed him as a (head) teacher, but ultimately could not prevent him from enrolling at the Rijksacademie in Amsterdam. He did arrange for his son to live with his friend J.A. Wormer, who owned a Christian bookshop on Kalverstraat.

Mondrian Sr. also taught drawing at school and made lithographic prints with historical and biblical scenes. He was a member of the Dutch Reformed Church and had all his children baptized in that church.