Siegfried "Sigi" Terpoorten (born September 15, 1971, in Munich) is a German actor.

After completing an apprenticeship as an electronics technician at Siemens, Siegfried Terpoorten pursued his acting training at the University of Music and Performing Arts Hamburg and at the Otto Falckenberg School in Munich. His first theater engagements took him to the Schauspielhaus Hamburg under the artistic direction of Frank Baumbauer, and later—together with Stefan Bachmann—to the Schauspiel Basel.

Terpoorten gained his first on-camera experience at the Hamburg Film Studies program under the direction of Hark Bohm. During this time, he collaborated with, among others, Kilian Riedhof and Marcus Hägg. He became known to a wider audience through the ARD television series *4 gegen Z*. Further television appearances followed in series such as *Tatort*, *SOKO Leipzig*, and *Ein Fall für zwei*, as well as in the two-part miniseries *Eine Liebe in Saigon*, alongside Désirée Nosbusch.

Terpoorten also appeared in feature films, including *Der Schuh des Manitu* and *Erkan und Stefan*. From 2006 to 2007, he played the lead role of Chief Inspector Mark Brenner in the Sat.1 crime series *Stadt, Land, Mord*. In 2010, he founded a film production company in Zurich and has since focused increasingly on his work as a producer. Terpoorten is married to actress Barbara Terpoorten-Maurer and has two children.