The Gunners have decided to sell the 28-year-old and talks with Villa over a deal are continuing, with an agreement likely to be reached in the next week.
Martinez earned rave reviews for his performances over the closing weeks of last season and started for Arsenal in last month’s Community Shield victory over Liverpool.
But the Argentine is not guaranteed the No.1 shirt at the Emirates with Bernd Leno poised to return from injury for this weekend’s Premier League opener against Fulham.
Villa, by contrast, can offer Martinez a shot at first-team football with their No.1, Tom Heaton, not due to return from a knee injury until after the October international break.
Reports claim personal terms have already been agreed and the biggest sticking point to the deal may be Arsenal’s wish to bring in a replacement before selling.
Brentford’s David Raya is their preferred target but the west London club, as Villa discovered during their efforts to sign Ollie Watkins, drive a hard bargain.
Watkins became Villa’s second signing of the window when he joined earlier this week for a club record £28m fee.
Having also spent £16m on right-back Matty Cash from Nottingham Forest, boss Dean Smith is keen to add another forward, midfielder and potentially a winger before next month’s deadline.