William Frederik Duntzfelt (12 June 1792 – 12 October 1863) was a Danish merchant.

His maternal grandfather was the wealthy merchant Frédéric de Coninck.

He continued the family firm after his father's death in 1809 and was granted citizenship as a merchant in 1812.

He was awarded the title etatsråd in 1857 and the Order of the Dannebrog in 1840. on 13 October 1814 in the Reformed Church in Copenhagen, Duntzfelt married to Bertha Christmas (1797–1872), daughter of ship captain John Christmas (1753–1822) and Johanne Marie Heinrich (1771–1808).

Duntzfelt died on 12 October 1863 and is buried in Assistens Cemetery.