The Prime Minister spent Saturday evening speaking to world leaders to explain why Britain had joined forces with France and the U.S. and will insist the three nations are "not alone" in believing it was the "right thing to do".
May said the aim was to deter the Syrian regime authorities from further use of chemical weapons and to send a message to the wider world that it was unacceptable to use such weapons.
Four Royal Air Force Tornado GR4s joined the co-ordinated missile strikes at 2am, launching Storm Shadow missiles at a base 15 miles west of Homs.
She declined to say whether Bashar al-Assad should stay in power and said talks with allies would continue on finding a political solution to the civil war.
"And the world said "enough" to the use of such weapons".
"The facility which was struck is located some distance from any known concentrations of civilian habitation, reducing yet further any such risk", the MoD said in a statement. Britain has accused Russia of being behind last month's nerve agent attack on former Russian spy Sergei Skripal and his daughter in Salisbury, southern England, a charge Moscow has rejected.
Jeremy Corbyn, the Labour leader, described the military action as "legally questionable" and said it should have been authorised by parliament.
"This persistent pattern of behavior must be stopped - not just to protect innocent people in Syria from the horrific deaths and casualties caused by chemical weapons but also because we can not allow the erosion of the worldwide norm that prevents the use of these weapons".
"It is in our national interest to prevent the further use of chemical weapons in Syria - and to uphold and defend the global consensus that these weapons should not be used".
Theresa May will pre-empt planned opposition motions by applying to the Speaker for a debate herself "to give the House an extended opportunity to discuss the military action".
Opposition Labour leader Jeremy Corbyn had said Britain should press for an independent United Nations -led investigation into the suspected chemical attack in Douma rather than wait for instructions from Trump on how to proceed.
Yesterday Prime Minister Theresa May insisted the military action was "legal" and defended the decision to go ahead without securing the backing of Parliament.
"Bombing can not substitute for diplomacy", he said.
He reiterated that Canada condemns the use of chemical weapons in Ghouta.
The Syrian regime has a history of using chemical weapons against its own people in the most cruel and abhorrent way.