The pair, who have been an item on the ITV2 dating programme since very early on, have taken a step ahead of fellow contenders Camilla Thurlow and Jamie Jewitt, according to a couple of bookmakers.
Cetinay and Davies' odds, according to Coral, are currently at 6-4 - the same as at William Hill.
Coral's spokesman John Hill said: "As the final looms, Kem and Amber have become the new favourites to take the top prize as they have attracted the most bets over the last couple of days. However, Jamie and Camilla are not too far behind in the betting and have been popular throughout the series."
Bookmaker Ladbrokes is offering odds of 7-4 for Cetinay and Davies, the same as they are offering for Thurlow and Jewitt.
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"Kem and Amber have spent much of the series as outsiders, but the latest odds suggest we could be in for a dramatic climax to the hit show," Ladbrokes' Alex Apati said.
Viewers have seen Cetinay and Davies' relationship go through several highs and lows throughout the programme's seven-week run, most dramatically when Cetinay chose to recouple with Chyna Ellis for a short while.
In recent weeks, they have appeared to be enjoying a smooth romance.
Newer couple Thurlow and Jewitt are second in the running at both Coral and William Hill, both offering odds of 7-4.
On-off twosome Chris Hughes and Olivia Attwood are third most likely to win Love Island, with all three bookmakers putting them at 5-2.
Previous show favourites Marcel Somerville and Gabby Allen have slipped in popularity at 12-1 across the board, while Montana Brown and Alex Beattie are bottom of the pile at 25-1.
Voted for by the public, the winning couple - who will receive a £50,000 to be shared between them - will be revealed in Monday's episode, on ITV2 at 9pm.