Peter J. Rousseeuw (born 13 October 1956) is a Belgian statistician known for his work on robust statistics and cluster analysis.

He obtained his PhD in 1981 at the Vrije Universiteit Brussel, following research carried out at the ETH in Zurich, which led to a book on influence functions.

His former PhD students include Annick Leroy, Hendrik Lopuhaä, Geert Molenberghs, Christophe Croux, Mia Hubert, Stefan Van Aelst, Tim Verdonck and Jakob Raymaekers.

[2][4][5] He proposed the Least Trimmed Squares method[6][7][8] and S-estimators[9] for robust regression, which can resist outliers in the data.

The work on cluster analysis led to a book titled Finding Groups in Data.

In 2024, he received the Gottfried E. Noether Distinguished Scholar Award of the American Statistical Association.