Longoria, 40, announced the news on Sunday when she shared a photo of the couple kissing in a desert in Dubai.
"Ummmm so this happened....#Engaged #Dubai #Happiness," she wrote."
In the photo, the actress is seen wearing a stunning ruby and diamond ring.
Longoria and Baston, 47, began dating in 2013.
"He's been sweeping her off her feet and courting her like a proper gentleman," a source told PEOPLE of their budding romance in 2013.
The Desperate Housewives star has gushed about her new fiancé in the past, praising both his mind and his personal style.
Pascal Le Segretain / amfAR15 / WireImage
"I'm attracted to humor and intellect in a man," Longoria told PEOPLE in 2014. "Let me tell you, I'm very lucky in my life."
Longoria's friend Ana Ortiz gave her stamp of approval in September.
"They're a gorgeous couple, and I've never seen her happier," the Devious Maids star told PEOPLE. "I am so thrilled that she has someone who is not intimidated by her and who is not afraid by her power, her beauty, her friendship and her drive."
Longoria was previously married to actor Tyler Christopher from 2002 to 2004. Her second marriage to NBA star Tony Parker ended when the couple split in 2011.