The deal for the France forward will eclipse the Gunners’ previous record transfer of £42.5m for Mesut Ozil in 2013.
Lyon owner Jean-Michel Aulas yesterday denied Lacazette was already in the capital and claimed Arsenal’s first offer had fallen short.
But Arsenal believe they have struck a deal in a major boost to Arsene Wenger.
Wenger wants to bolster his ranks with Lacazette, also wanted by Atletico Madrid having scored over 20 Ligue 1 goals in each of his last three seasons for Lyon, in the first part of his revamp.
Olivier Giroud and Theo Walcott, both wanted by West Ham, could now move on but it remains to be seen whether the arrival of Lacazette, 26, will have an impact on the future of contract rebel Alexis Sanchez.
Bayern Munich boss Carlo Ancelotti has confirmed his interest in the Chile striker but insists his club will not pay “crazy money”.
Ancelotti said: “If an opportunity comes up, the club will be ready. There are lots of rumours. Alexis is a great player but not the only one in the world. I like Alexis.
“There are possibilities in the transfer market, which can be in many direction. I believe that the market is currently somewhat crazy, and Bayern is not a crazy club.
“I know the culture of this club and will not ask for any players for whom the club has to spend crazy sums, but if there are opportunities, why not?”
Sanchez has refused to sign a new deal at Arsenal and is out of contract next summer. Yet while Manchester City have shown interest, Wenger will refuse to sell his man to any of the Gunners’ Premier League title rivals.
