Dietrich, Count of Oldenburg, German noble (b.c. 1398)

Dietrich or Theoderic of Oldenburg (c. 1398 – 14 February 1440) was a feudal lord in Northern Germany, holding the counties of Delmenhorst and Oldenburg. He was called "Fortunatus", as he was able to secure Delmenhorst for his branch of the Oldenburgs.

Dietrich was the father of Christian I of Denmark, who would go on to start the current dynasty of the Danish throne.