Cambridge Mayor E. Denise Simmons, the country’s first openly lesbian mayor, married her longtime partner Mattie B. Hayes Sunday.

Colleagues, city councillors, friends and family attended the gathering, which took place at Central Square’s Saint Bartholomew’s Episcopal Church at 2 p.m.

“It was a joyous affair,” said Neal Alpert, the city’s director of constituent services. “It was smiles all around.”

The two have been together for seven years and have known each other since they met in graduate school 20 years ago, Simmons said yesterday.

The wedding was officiated by Reverend Irene Monroe, a black lesbian minister and close friend to both Simmons and Hayes.

Monroe said the wedding was historic, since it represented the first time a predominantly African-American church in Cambridge has allowed same-sex marriage.

“I was honored to be a part of it,” she said.

Simmons is also raising her three grandchildren, who attend Cambridge public schools, making the wedding an occasion that “completed the family,” said Rosaleah Brown, deputy assistant to the mayor.

Though Simmons and Hayes do not have any concrete plans for a honeymoon, they have “lots of ideas,” Simmons said.

She described the occasion as historic, celebratory, and familial.

“It’s a privilege to wed the person you love and want to spend the rest of your life with,” Simmons said of her wife, who is an administrator with a program that aims to aid young women in the juvenile detention system in New York.

“We had love, and now we have that legal document as well,” she said.