American talk show host Ellen DeGeneres and her actress girlfriend Portia De Rossi will marry at their Beverly Hills home on Saturday night.

The lesbian couple, who have been dating since December 2004, announced their engagement in May shortly after the California Supreme Court made same sex civil partnerships legal.

DeGeneres, 50, and De Rossi, 35, are planning a small, private ceremony in front of 20 family and friends at their £15million estate.

Wedding belles: Ellen DeGeneres and Portia De Rossi will marry at their Beverly Hills estate on Saturday night

De Rossi will walk down the aisle in a flowing Zac Posen gown, while DeGeneres is expected to wear a trouser suit.

Speaking of their planned nuptials earlier this year, the multi-Emmy winning TV presenter said: 'It's something that we've wanted to do and we want it to be legal and we are very, very excited.

'I think someday people will look back on this like women not having the right to vote and segregation and anything else that seems ridiculous that we don't all have the same rights.

'Planning a wedding is very stressful. It's crazy. My gardener is now invited.'

The laid-back couple also refused to create a wedding list, insisting they have everything they need.

De Rossi said: 'We don’t have a registry, we don’t need anything. We’ve been blessed enough, we don’t need any gifts from anybody.'

The pair began dating in 2004 after splitting from their previous partners - Ellen had been in a relationship with photographer Alexandra Hedison, while De Rossi dated Francesca Gregorini, daughter of former Bond girl Barbara Bach.

DeGeneres was also in a high-profile relationship with actress Anne Heche, who she started dating soon after 'coming out' on the cover of Time magazine in 1997.

Australian-born De Rossi, who was born Amanda Lee Rogers, launched to fame playing ice queen Nell in Ally McBeal and also starred in the critically-acclaimed comedy Arrested Development, which was cancelled in 2006.

More recently, she has played alternative medicine specialist Olivia Lord in Nip/Tuck, who embarks on a lesbian affair with Joely Richardson's character Julia McNamara.