Célestin Demblon (19 May 1859 – 13 December 1924) was a Belgian socialist politician, teacher and writer, known for his anti-clerical views and his promotion of Francophone Walloon culture.

Demblon embarked on a political career in 1894, standing in the legislative elections of that year against the former Liberal prime minister Walthère Frère-Orban as a Socialist candidate.

His distaste for the Catholic church was expressed in pamphlets with titles such as "La pornographie cléricale", which provoked a debate in the legislature about Demblon's claim that the Bible was full of pornographic passages.

In 1887 he objected to official support for "patois", writing that "the powerful and lucid young people who have just appeared as if by magic in Wallonia will most certainly take their place enthusiastically before the great organ of the French language"[3] In 1896, during a major strike, Demblon created the Fédération liégeoise du Parti ouvrier belge (Liege Federation of the Belgian Workers Party), becoming its first member.

[1] The POB (Parti ouvrier belge), as it was known, was designed as an alliance of radical groups promoting a consensus socialist political vision.

After the war he revived his role as a leader of the Fédération liégeoise, but soon fell out with other members of the leadership, as he showed increasing sympathy for Communism, in particular expressing support for the Russian Revolution.

'Social security' has been thrown by the bourgeoisie at the head of the workers in panicked fear of Bolshevism in our country, as one throws a bone to a dangerous dog.

"[5] He was expelled from the POB on a technicality (failure to promptly pay membership fees), as the leadership were unable to secure enough support for his removal from ordinary members.