Christian Ulrik Kastrup (1784–1850) was a Norwegian jurist, military officer and politician.
A jurist by education, from Stavanger, he worked as a military officer until 1811, when he became chief of customs in Vardø. In 1817 he became fut in the district Nordhordland og Voss. He was elected to the Norwegian Parliament from Søndre Bergenhus in 1821, 1822 and 1824. Political parties did not exist at the time.
He became County Governor of Finnmark in 1828, of Rogaland in 1829 and of Nordre Bergenhus (now: Sogn og Fjordane) 1833. Originally governing from the market town of Bergen, he moved to Lærdalsøyri in 1840, becoming the second Sogn og Fjordane county governor to actually live in the county. He held the position until 1844.
| Preceded by Johan Caspar Krogh |
County Governor of Finnmark 1828–1829 |
Succeeded by Ulrik Fredrik Cappelen |
| Preceded by Peder Martinius Ottesen |
County Governor of Rogaland 1829–1833 |
Succeeded by Gunder Aas |
| Preceded by Fredrik Ris |
County Governor of Sogn og Fjordane 1833–1844 |
Succeeded by Hans Tostrup |