William Wrenn (born March 16, 1991, in Anchorage, Alaska) is an American defenceman playing for the Portland Winterhawks of the Western Hockey League.
He played for the USA Hockey National Team Development Program from 2007 to 2009. Wrenn then joined the Denver Pioneers of the NCAA. He suffered a hip injury in his freshman year.
In his sophomore year (2010-11) Wrenn found himself as one of seven regular defencemen on the Pioneers. Dissatisfied with his ice time, Wrenn then jumped to the Winterhawks in January, 2011.
The San Jose Sharks chose him 43rd overall in the 2009 NHL Entry Draft.