Three same-sex couples arrived at dawn at Brighton Town Hall to be among the first in the UK to register their intention to form civil partnerships.
Alan Bond and Derek Peacock will tie the knot on 21 December
Debbie and Elaine Gaston, Gino Meriano and Mike Ullett, and Roger Lewis and Keith Willmott-Goodall were waiting when the register office opened.
The couples simultaneously registered their intentions at 0730 GMT in the self-styled gay capital of the UK.
They will have a joint ceremony on 21 December after a 15-day waiting period.
Brighton and Hove City Council said the six were believed to be the first in the country to register their intention.
Registrar Debra Reynolds said the couples had been waiting for this day for a long time.
"They were very emotional, very excited, quite overwhelmed," she said.
"We have all been talking about this for months and now it's finally here it's almost like a dream... being able to make a difference to so many people's lives."
The Rev Debbie Gaston, 46, a minister at Brighton Metropolitan Community Church, has been with teacher Elaine Gaston, who changed her name by deed poll, for 16 years.
She said it was wonderful to be able to make the registration.
"We were aware it was history in the making.
"I believe it's God that has opened up this door for the civil partnerships to happen.
"We are going to have a Christian blessing at the start of our reception," she said, adding that one day she hoped the Church would accept same-sex marriages.
The East Sussex council received 510 provisional bookings for civil partnership ceremonies before the Civil Partnerships Act became law on Monday.
Bone marrow transplant
It was expecting about 20 couples to officially register their intention to form a partnership through the day.
It said approximately 20% of the city's residents lived in same-sex households and was expanding its register office to cope with extra demand.
Derek Peacock, 62, registered his intention with his partner of 32 years, Alan Bond, 58.
Mr Peacock said they had feared Mr Bond, who has cancer, might not live to see this day.
"He's had a bone marrow transplant and is in remission," he said.
"It's really been quite traumatic for us."
The couple, who have worked together in property management for 20 years, said their partnership ceremony on 21 December would be a "double celebration".
"We have waited years and years for this," said Mr Bond.