An Indian Muslim preacher has been banned from entering the UK for his "unacceptable behaviour", the home secretary says.
Zakir Naik, a 44-year-old television preacher, had been due to give a series of lectures in London and Sheffield.
Theresa May said that visiting the UK was "a privilege, not a right".
The home secretary can stop people entering the UK if she believes there is a threat to national security, public order or the safety of citizens.
That includes banning people if she believes their views glorify terrorism, promote violence or encourage other serious crime.
However, somebody cannot be banned just for having opinions that other people would find offensive.
Ms May said: "Numerous comments made by Dr Naik are evidence to me of his unacceptable behaviour.
"Coming to the UK is a privilege, not a right and I am not willing to allow those who might not be conducive to the public good to enter the UK.
"Exclusion powers are very serious and no decision is taken lightly or as a method of stopping open debate on issues."
This is the first person who has been excluded from the UK since Ms May became home secretary last month.
Mr Naik is based in Mumbai (Bombay) where he works for the Peace TV channel.
He was due to address events at Sheffield Arena on 25 June and Wembley Arena on 26 June.
The BBC's Sanjiv Buttoo says that he is recognised as an authority on Islam but also has a reputation for making disparaging remarks about other religions.
Peace TV itself describes him as "a medical doctor by professional training... and a dynamic international orator on Islam and comparative religion".
"Dr Naik clarifies Islamic viewpoints and clears misconceptions about Islam using the Koran," the channel's website says.
A spokesman for Mr Naik said it was "deeply regrettable" the UK government had "bowed to pressure" from certain groups to exclude him.
He said Mr Naik had been holding talks in the UK for 15 years and the decision to bar his entry was disappointing.