Nicole Richie is not only pregnant but also engaged, according to spywitnesses at Page Six.

“The Simple Life” star reportedly showed up for the Yves Saint Laurent Pool Party to benefit Center Dance Arts at the Beverly Hills Hotel on Thursday night wearing a huge diamond engagement ring.

“It was one big rock surrounded by more diamonds,” says an NYP snitch. Joel was reportedly “overly attentive to her – keeping his arm around her all night – and repeatedly asked her if she was OK.”

Reforming partygirl Nicole even refused all alcohol, which a snitching source called “a first for her.”