Sweder III of Zuylen of Abcoude, Lord of Gaasbeek, Putte, Strijen, Wijk, and Durstede ( c.1340 – 22 or 23 April 1400) was a councillor to Joanna, Duchess of Brabant and became infamous for ordering the murder of Everard t'Serclaes.

He was one of the six mediators that Duchess Joanna chose to negotiate for peace with William I of Guelders and Jülich.

[1] Seeking to annex the bailiwick of Rhode, part of the Quartier de Bruxelles [fr], he had the Brussels alderman Éverard t'Serclaes assassinated in 1388, because opposed his plans.

Sweder died on 12 April 1400, on his way to the celebration of the Holy Year in Rome.

A giant in his likeness him takes part in carnival parades in several towns of Walloon Brabant.