Halfdan Wilhelmsen (March 11, 1864 – November 18, 1923) was a Norwegian shipowner and consul. Wilhelmsen was born in Tønsberg, the son of the shipowner Wilhelm Wilhelmsen and his wife Catharina Fredrikke Lorentzen. After graduating from business school, he was employed in brokerage and shipowners' offices in England, Germany, and France. In 1887 he became the co-owner of his father's company, Wilh. Wilhelmsen. He built this up into the largest shipping company in the Nordic region, and he was one of the pioneers in the transition from sailing ships to steamships.