- General counsel Patrick Stewart will take over as chief executive on an interim basis while the club decides on a permanent replacement.
- Arnold first joined United in August 2007 and acted as the club's managing director from 2013 until he replaced Woodward.
Manchester United chief executive Richard Arnold is set to leave the club, BBC Sport understands.
The 52-year-old replaced Ed Woodward as United's most senior executive in February 2022.
His departure, yet to be officially confirmed, comes as Sir Jim Ratcliffe's Ineos Group prepares to finalise its purchase of a 25% stake in the Premier League giants.
It is understood no announcement on Ratcliffe's deal is expected today.
Ineos Group is set to pay around £1.25bn for their minority purchase, which is expected to be ratified during November's international break.
General counsel Patrick Stewart will take over as chief executive on an interim basis while the club decides on a permanent replacement.
Stewart has represented United at recent Premier League and European Clubs' Association meetings.
There will be a gap of six to eight weeks between the announcement of the Ratcliffe deal and its confirmation by the Premier League, during which time the British billionaire will be unable to contribute to club operations.
Arnold first joined United in August 2007 and acted as the club's managing director from 2013 until he replaced Woodward.
He recently oversaw United's significant sponsorship agreements with Adidas and Qualcomm, but was criticised for his handling of the situation surrounding forward Mason Greenwood.
Arnold initially hinted to staff that the former England international was set to be reintegrated with the first team after serious charges against him including attempted rape and assault were dropped, before deciding the player had to leave Old Trafford.
In June 2022 he met with some fans in his local pub to head off a planned protest outside his house following what he described as "a nightmare" season in which manager Ole Gunnar Solskjaer was sacked and United finished sixth.
Last summer Arnold oversaw the appointment of current manager Erik ten Hag, who delivered the club's first trophy in six years by winning the Carabao Cup in his debut season.
However, United have endured a difficult start to the 2023-24 campaign, losing nine of their first 18 games in all competitions.