The Fancy hitmaker, who has been linked to Montana since the summer (16), invited around 60 of the birthday boy's friends to mark the occasion with a boat bash in California's Marina Del Rey.
She also had a helicopter on hand to fly the couple to the party, where waiting guests included Drake, Sean 'Diddy' Combs, the rap mogul's girlfriend Cassie, and model Amber Rose, reports TMZ.com.
The extravagant event also featured a fireworks show, which lit up the night sky.
The party took place hours after French had spent the day hanging out with an elephant, which was delivered to his Los Angeles mansion and placed in his backyard.
He shared an Instagram shot of himself posing beside the beast, which had jewellery on its head and around its ankles, and captioned it, "I love animals more than people!! Happy bday (sic) to me positive vibes at the Casa (home)".
Under another snap of French standing next to the animal, he wrote: "Turn your life to a life time vacation. Grinded all day so I can ball tomorrow bday officially here all praise due to the most high (sic)".
Iggy also posted a picture of herself petting the elephant, but the couple's actions did not sit well with fans - many attacked the stars for engaging in a form of animal cruelty.
"That precious creature has chains around its ankles. Don't like this," wrote one concerned follower, while another added, "How could u enjoy an elephant dancing for u (sic)???? Poor thing".
One animal rights activist blasted Montana as a "f**king psycho" for adding to the "poor elephant's misery" with his Instagram posts, while another follower pleaded, "Please educate yourself on what happens to elephants before they can perform tricks. There's other ways to have fun on your birthday without exploiting animals. What a dangerous message to send to your followers!"
The stars have yet to respond to the backlash.
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