The supermodel has been spotted showering Doronin with kisses while spending time on his luxury yacht in St Tropez this week.
Campbell met the property tycoon at the Cannes Film Festival in May and their relationship progressed quickly. She introduced Doronin to her 12 closest friends at a special dinner party in the South of France last month.
One guest, Brazilian writer Bruno Astuto, told the Daily Mail: "She said it was love at first sight and he is completely in love with her. Watching them look deeply into each other's eyes, it was obvious that this is a very serious affair.
"He thinks she is a goddess and Naomi believes she finally has found the right man. She is now planning a really big party for Vlad, where we hope they will announce their engagement."