Johnson was seen sporting a massive emerald-cut ring on her left hand while shopping in West Hollywood, Calif., on Monday, December 14.
The 31-year-old and Coldplay frontman have yet to weigh in on the speculation, as they have remained extremely private about their three-year relationship. Despite keeping their romance on the down-low, the 50 Shades of Grey actress said in 2018 that she was not going to talk about her relationship but that she is "very happy."
Page Six was the first to publish the photos of Johnson donning the massive rock.
The lovebirds first fueled romance rumors back in December 2017 when they were spotted together on a romantic trip to Israel. They were more recently seen out in March for a rare date night in Los Angeles, Calif., and have since been spotted in Malibu and the Hamptons.
Martin was previously married to Gwyneth Paltrow for 11 years before the duo announced their "conscious uncoupling" in March 2014. The former flames share children Apple, 16, and son Moses, 14, and have remained close over the years as they continue the next chapters of their lives.
Even Paltrow is rooting for the "Yellow" singer to tie the knot with the brunette beauty. "I love her," Paltrow said in an interview earlier this year. "I can see how it would seem weird because it's sort of unconventional. I just adore her. I always start to think of the ampersand sign — what else can you bring in, instead of being resistant to or being made insecure by? There's so much juice in leaning in to something like that."
While talking about her "unconventional" family, Paltrow got candid about the struggles of co-parenting. "Chris and I committed to putting the kids first, and that's harder than it looks because some days you really don't want to be with the person that you are getting divorced from," Paltrow previously confessed on The Drew Barrymore Show in September.
"But if you're committed to having family dinner, then you do it," the mother of two said. "You take a deep breath, and you look the person in the eye, and you remember your pact, and you smile, and you hug and you recommit to this new relationship that you are trying to foster. … I really wanted my kids not to be traumatized, if it were possible."
Johnson and the English musician, 43, took a brief pause in their relationship in mid-2019 but reconciled that August. Paltrow, 48, went on to marry her second hubby, Brad Falchuk, in September 2018.