Lester Cohen / WireImage 1 / 6
Lester Cohen / WireImage 1 / 6

Nicole Richie and her boyfriend of four years, Joel Madden, said "I do" in a winter-themed ceremony Saturday in Beverly Hills, UsMagazine.com has confirmed.

Held at the home of Nicole's father, Lionel, the black-tie evening event was attended by approximately 150 family members and friends, including Khloe Kardashian and Samantha Ronson. One other guest: an elephant! Around 5:40 p.m., observers spotted an elephant arriving in the driveway; the animal was led into a white tent with other revelers.

The bride's BFF, Masha Gordon, served as maid of honor, while the couple's 2-year-old daughter, Harlow, was the flower girl. (The couple also have a son Sparrow, 15 months.)

Richie, 29, strived to get every detail right for her big day -- putting extra special thought into her gown. Just days before the wedding, Richie remained torn over two designs: Marchesa and a vintage Chanel. In fact, she jetted off to New York City Dec. 3 for a final fitting at Marchesa with her stylist, Simone Harouche. "A lot of thought went into her dress -- it was a priority for her," a source explains.

Why the winter theme?

"Nicole is obsessed with the season," a pal tells Us of the designer and author, who confirmed her engagement in February. (Her daughter's middle names are Winter Kate, also the title of her clothing line).

"[The fete is] less about Joel and Nicole getting married and more about having a party," another pal told Us of the soiree, planned by Mindy Weiss. "The spirit is that it's a celebration and it's very low-key."

Though the couple has finally made their union official, Richie and Madden say they've long felt like husband and wife.

"We're really focused on our family, and...we already feel kind of married, you know?" Madden, 31, told Larry King in 2009. "Our family system that we have down, we feel like this is a real family and marriage, one day it will come."

Richie's father, who walked his daughter down the aisle, is equally as taken by their love.

"My happiness for Nicole and Joel knows no boundaries," the "All Night Long" crooner says. "They have given me two beautiful grandchildren, Harlow and Sparrow, and have proven to be great parents. I am not sure who is luckier, Nicole and Joel to have each other, or me, to have both of them in my life."

More on Wonderwall:

The Year in Hookups and Breakups

Best celeb weddings of the season

What do Harlow and Sparrow want for Christmas?

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