Lennart Stekelenburg (born 22 October 1986) is a Dutch swimmer who specialises in breaststroke.

Stekelenburg made his international senior debut at the 2005 World Aquatics Championships in Montreal, Quebec, Canada where he was eliminated in both 50 m and 100 m breaststroke.

In the following years he swam several European Championships making his best performance at the 2008 European Aquatics Championships in Eindhoven in his home country the Netherlands, ending up 6th in the 50 m breaststroke final after swimming a national record in the semi-finals.

Stekelenburg qualified for the 2009 World Aquatics Championships during the Swim Cup Eindhoven 2008, in early December, with a national record at the 100 m breaststroke.

This biographical article related to a Dutch swimmer is a stub.