Manchester United are reportedly considering plans to extend the capacity of Old Trafford to 88,000 from its current 75,643.
According to Mike Keegan of MailOnline, the additional 12,000-plus seats would be made available by extending the Sir Bobby Charlton Stand, the former South Stand, where the directors' box and dugouts are located.
Keegan added the plans have been prompted by the fact new facilities for disabled fans are set to reduce Old Trafford's capacity to around 73,300 by 2020.
United's home ground was last expanded in 2005 and 2006 when additional tiers to the north-west and north-east quadrants saw the capacity increased beyond the 70,000 mark.
Old Trafford's standing as the biggest ground for a Premier League club has never been really threatened in recent years.
Arsenal's Emirates Stadium is the second largest permanent residence of an English top-flight club and holds just over 60,000.
Meanwhile, Tottenham Hotspur are playing at the 90,000-capacity Wembley Stadium for the 2017-18 season while their new home ground is built.
An increase to 88,000 would see Old Trafford surpass almost every other stadium in Europe in terms of capacity, leaving it behind only Barcelona's Camp Nou and Wembley.