Tjeldsund is a municipality in Nordland county, Norway. It is part of the Ofoten traditional region. The administrative centre of the municipality is the village of Hol i Tjeldsund. Tjeldsund was separated from the municipality of Lødingen in 1909.
Villages in Tjeldsund include Fjelldal and Ramsund. Norges Brannskole (The Norwegian education and training center for firemen) is situated in the municipality. Marinejegerkommandoen is based at Ramsund.The municipality is named after the Tjeldsundet strait between Tjeldøya and Hinnøya. The first element is the (uncompounded) Old Norse name of Tjeldøya (Tjöld or Tjalda) and the last element is Sund which means "strait" or "sound". The name of the island is probably derived from tjald which means "tent" or tjaldr which means "oystercatcher (Haematopus ostralegus)".