British millionaire Alexander announced the news on Thursday on Instagram with a loved up photo of the couple and the caption, "Thank you for making me a very, very happy boy. I look forward to a lifetime of loving you and learning from you @mariasharapova." He added a ring emoji.
WATCH: Maria Sharapova announces engagement to Alexander Gilkes with romantic video
Fans have since rushed to congratulate the pair with 277 well wishes in the comments (at the time of writing), and thousands of likes.
Alexander shared a photo with Maria on Instagram
Maria also shared two photos along with two videos to announce the news, and wrote, "I said yes from the first day we met [heart emoji]. This was our little secret, wasn't it? @gilkesa."
Maria posted a selfie of herself and Alexander
The images Maria shared included a selfie of the couple, a photo of their shadows as they walked, and two videos: one of their feet swinging and another of Maria dancing while Alexander sat on a bench.
Maria posted a second image of the couple
Maria confirmed that she was dating Alexander in October 2018, but the pair were first linked in January of the same year after being pictured together at Los Angeles' LAX airport.
Alexander, 40, is believed to have become friends with Prince William while studying at Eton. He was also a guest at Princess Eugenie's wedding in 2018. He took to Instagram to mark the occasion with a post that read: "The start of the post wedding waddle home with a head full of elated memories and a belly full of bubbles from the happiest day of celebrations for Eugenie and Jack."
Alexander's younger brother Charlie Gilkes is also rumoured to have been in a relationship with Pippa Middleton during their time at Edinburgh University.
Alexander is the co-founder and president of Paddle8, an online auction house.
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