John David Alexander (born 1959) is a retired United States Navy vice admiral and naval flight officer who last served as the 29th commander of the United States Third Fleet from September 15, 2017 to September 27, 2019. Prior to that, he held command tours as the commanding officer of USS Abraham Lincoln (CVN-72) from January 2010 to September 2012, and commanding officer of the USS Juneau (LPD-10) from 2006 to 2007.