Franz Seraph von Dietrichstein (Czech: František Serafín z Ditrichštejna, 22 August 1570 – 19 September 1636), of the Austrian and Moravian House of Dietrichstein, was Prince of Dietrichstein, Archbishop of Olomouc, Governor (Landeshauptmann) of Moravia and a Cardinal.
Dietrichstein was born on 22 August 1570 in Madrid, the 8th of 12 children born to Adam von Dietrischstein, the Holy Roman Empire's then-ambassador to Spain.
He studied in Vienna and Prague. Then in 1588, at age 18, he moved to Rome to study at the Collegium Germanicum. While in Rome be befriended Cardinal Ippolito Aldobrandini who was elected pope in 1592 and took the name Pope Clement VIII. Dietrichstein became the new pope's chamberlain and worked to represent the interests of his native Bohemia as canon of the cathedral chapters of Olomouc, Wroclav, Passau and Leitmeritz.
Dietrichstein was ordained in 1597 and then elevated to cardinal only two years later, in 1599, with an appointment as cardinal-priest of San Silvestro in Capite. In May of that same year he was elected as Archbishop of Olomouc, though his election was opposed by members of the local cathedral chapter. He was consecrated by the pope himself, with special dispensation for having not reached canonical age (he was only 29 at the time). According to historian Ludwig von Pastor, Dietrichstein became the, "soul of all Catholic undertakings in Moravia". It was apparently due to Dietrichstein's zeal that protestant reformer Karl von Zierotin was forced into early retirement.