According to Daily Mail, Morgan Brown was seen on Sunday in Malibu wearing the diamond ring. See the picture on the Daily Mail.
Butler and Brown, an interior designer and former model, have reportedly been dating since last summer.
In December, the two were photographed kissing at a football game in New Orleans.
Prior to dating Brown, Butler was linked to Lindsay Lohan, Jessica Biel, Jennifer Aniston, Brandi Glanville and Madalina Ghenea.