“My love. My life. My family. My future,” Lohan wrote on her verified Instagram account, tagging Shammas and adding a diamond ring emoji.
The post features four low-resolution photos showing the two in a happy embrace, including a look at Lohan’s sparkling engagement ring.
Lohan, now 35, is best known for her star performances in “The Parent Trap,” in which she played identical twins, and the teen comedy “Mean Girls.”
Once a fixture of the tabloid media, she had several prominent legal and personal struggles about a decade ago, but she has had a lower public profile in recent years. She still has an Instagram following of 9.7 million people, while Shammas has a private profile with just under 600 followers.