Guillaume Delcourt (31 March 1825 – 2 February 1898) was a Belgian Royal Navy officer, navigator, naval engineer and maritime advisor to King Leopold II.

His father Napoleon Joseph Delcourt, a brewer born in Ath, was injured while fighting for the Belgian Revolution in 1830[3] and died three years later in Antwerp on 30 July 1833.

After the death of his parents, he was raised by his mother's sister, Jeanne Wittouck, and her husband, Jean-Louis Van Dievoet, Secretary of the Court of Cassation.

During his return, his ship silted up, found itself in a bad position and took shots from partisans of Mayoré but was saved by the Africans who stayed loyal to the Belgians.

On the island of Gorée, the Belgians received a message from the consul of Belgium L. Bols-Wittouck, a cousin of Delcourt, that asked them to get back to Rio-Nunez rapidly, as the situation was worsening.