Wilhelm Martin Philipp Christian Ludwig Liebknecht (29 March 1826 – 7 August 1900) is a German social democrat and one of the principal founders of the SPD.

His political career is a pioneering project combining Marxist revolutionary theory with practical, legal political activity.

Under his leadership, the SPD grows from a tiny sect to become Germany's largest political party.

He is the father of Karl Liebknecht and Theodor Liebknecht.