The Belgium striker, 31, is expected to join the Italian club for a fee of about £30m on a permanent deal that will include a sell-on clause.
It remains possible the transfer could lead to Victor Osimhen moving in the opposite direction, with Chelsea preferring an initial loan deal for the Nigeria forward.
Napoli’s move for Lukaku has been driven by manager Antonio Conte, under whom the Belgian enjoyed two prolific seasons for Inter Milan from 2019 to 2021.
The striker rejoined Chelsea in 2021 for £97.5m but has spent the past two seasons on loan in Italy, first back at Inter and then with Roma.
His return to Stamford Bridge proved unsuccessful and he has not played for the Blues since May 2022.
Chelsea are looking to offload players as their senior squad has swelled to more than 40 after 11 signings this summer.
