Ndombele is not part of Antonio Conte’s plans and talks are progressing on a deal which would include an option for the Italian side to make the move permanent next summer for around £25million.
The Frenchman is said to like change, with Napoli set to compete for the Serie A title after finishing third last season and also able to offer Champions League football.
Ndombele joined Spurs from Lyon in 2019 in a club-record deal worth up to £65m but has rarely shown his best form in north London.
The 25-year-old made just nine Premier League appearances for Spurs last season and just two after Conte took over from sacked Nuno Espirito Santo in November.
He was sent back to Lyon on loan in January but returned to Spurs in the summer after a disappointing spell which saw the club finish eighth in Ligue 1 and fall to West Ham in the Europa League quarter-finals.
Ndombele was one of several players deemed surplus to requirements left out of Tottenham’s pre-season tour of South Korea and trained individually outside of the main squad.
It’s been a busy summer for Spurs, who have already made six new signings and expect Udinese defender Destiny Udogie to become the seventh. Spurs have agreed an initial fee of £15m for the 19-year-old, who will return to Udinese on loan for the rest of the season.
There remains a need to empty the bridges, with Giovani Lo Celso having joined Villarreal on loan earlier this week, while the club are also looking to move on to Sergio Reguilon and Harry Winks.