BBC accused of 'bias' over European election coverage - despite giving Nigel Farage prime interview slot
The Brexit Party leader said he had some sympathy with Mrs May, but that the Tory party had not learned its "lesson" over Brexit.
He tweeted: "It is difficult not to feel for Mrs May, but politically she misjudged the mood of the country and her party.
"Two Tory leaders have now gone whose instincts were pro-EU. Either the party learns that lesson or it dies."
It is difficult not to feel for Mrs May, but politically she misjudged the mood of the country and her party. Two Tory leaders have now gone whose instincts were pro-EU. Either the party learns that lesson or it dies.— Nigel Farage (@Nigel_Farage)May 24, 2019
Eurosceptic Mr Farage has long been a critic of the Government's negotiations on leaving the EU.
He has recently been rallying support for MEPs for his new Brexit Party, during which he has called for "change" in politics.
Mrs May announced her exit from Number 10 during an emotional speech on Friday morning.
She will resign as Tory leader on June 7, as pressure mounted over her handling of Brexit.
Mrs May will stay on in her role as PM until a new leader is decided upon.
In a public address in Downing Street, she said: "I will shortly leave the job that it has been the honour of my life to hold - the second female Prime Minister but certainly not the last.
"I do so with no ill-will, but with enormous and enduring gratitude to have had the opportunity to serve the country I love."