President Donald Trump once tweeted military intervention in Syria would be "foolish" and a waste of "powder".
More than 50 tomahawk missiles were fired from two US naval ships at 1pm (NZ time) targeting runways, aircraft and fuel depots.
Mr Trump called the airstrike a "vital national security interest", an apparent change of tune from his 2013 tweets, where he criticised then president Barack Obama and called military intervention "foolish".
Today's airstrike comes in response to a suspected chemical weapons attack in northwestern Syria on Tuesday, which killed at least 86 people including 30 children.
Mr Trump says it was a "horrible" attack that "choked out the lives of helpless men, women and children."
Mr Trump says he only targeted the area from which the chemical weapons attack was launched.