Sacha Baron Cohen and Isla Fisher have welcomed a baby boy – and his name is quite a mouthful.

The couple – who already have two daughters – quietly welcomed their first son into the world last month, at Cedars Sinai Medical Centre in Los Angeles.

And the birth certificate, published online by gossip website TMZ.com, shows his name is Montgomery Moses Brian Baron Cohen.

Sacha accompanies a heavily pregnant Isla to the Vanity Fair Oscars party in February (Evan Agostini/Invision)
Sacha accompanies a heavily pregnant Isla to the Vanity Fair Oscars party in February (Evan Agostini/Invision)

It was revealed last week that Isla and Sacha – who have been together since 2002 and married in 2010 – had had another baby, but the sex and name were unknown until now.

Montgomery will be a little brother for seven-year-old Olive and Elula, four.