In September 2022, the West Midlands outfit paid in the region of £13m to sign the Belgium international from Wolverhampton Wanderers.
However, Dendoncker has failed to match the level that he showed at Molineux, rarely being provided with opportunities in the Premier League.
The 28-year-old has made a total of just eight starts and 20 substitute outings during top-flight fixtures, his one goal coming against Manchester United during the recent Christmas and New Year period.
That has proven to be Dendoncker's solitary start in the Premier League during 2023-24, and 70 minutes followed during a 1-0 win over Middlesbrough in the FA Cup third round on January 6.
Nevertheless, rather than retain the services of the versatile defender and midfielder, boss Unai Emery has given the green light for Dendoncker to leave for Italy.
Dendoncker departs Villa on a temporary basis despite making five starts and 10 substitute outings in what could still prove to be a congested season for Villa.
As it stands, it is unclear whether Villa will try to sign a replacement, with Middlesbrough forward Morgan Rogers said to be their priority target before the end of the January window.
From Napoli's perspective, they are attempt to kick-start their season at a time when they sit down in ninth position in the Serie A standings.
Since the turn of the year, Pasquale Mazzocchi, Hamed Traore and Cyril Ngonge have already arrived from Salternitana, Bournemouth and Hellas Verona respectively.
Transfer expert Fabrizio Romano claims that the Serie A champions have the option to sign Dendoncker on a permanent basis for €9m (£7.68m) at the end of the season.