The Charlie’s Angels actress, 42, who has previously dated Justin Timberlake and Alex Rodriguez, amongst others, first stepped out with Madden, 35, in May of this year. And after a whirlwind seven-month romance the happy couple are ready to make things official!
"Everyone thinks it's wild but are so happy for them," one source told Us. "Benji always tends to fall in love easily, but this time it's for real and he landed a great girl. They obviously both make each other incredibly happy and there's nothing better than that." Find out more about Cameron and Benji's whirlwind romance.
In September, a friend of the couple revealed to Us that Madden (whose twin brother and bandmate is Joel Madden, husband of Nicole Richie), was keen to do things right when it came to his relationship with Diaz.
"He is more traditional then her," the pal said. "She really doesn't care about getting married but wants babies. He wants to get engaged and married first."
In fact the couple have Diaz's pal (and soon-to-be sister-in-law) Richie to thank for their happiness.
"I approve of anything that's going to make Benji happy," the mom-of-two told Watch What Happens Live's Andy Cohen back in July. Did she set them up? "Yes," she answered. "I'm going to take responsibility for everything!"
Another family member who will be skipping with joy about their happy news is Diaz's mom, who is a big fan of the heavily tattooed rocker.
"Billie has been gushing about Cameron's new relationship," a source told Us previously of the union. "She absolutely loves Benji and she hopes this is the man her daughter will finally settle down with."
Looks like mom got her wish!