Alistair Darby, who is currently chief operating officer at Marston's, will take up the top job at M&B in October.
He will become M&B's first permanent chief executive since Adam Fowle resigned back in March 2011.
M&G owns the All Bar One, Harvester, Toby Carvery and O'Neills chains, with more than 1,500 outlets overall.
Mr Alistair Darby will take over the chief executive role from Bob Ivell who has been combining it with his position as chairman on a stand-in basis since October of last year.
Mr Ivell said the appointment of Mr Darby had followed an "extensive and rigorous" search process.
He added: "I am confident that we have secured the right person for the role and that drawing on his wealth of operational and brand experience."

The Reds had their capacity reduced to zero earlier this month when the council revealed they did not have a required safety certificate holder.
The Championship club have now been granted their certificate but the City Ground will only be able to hold 24,357 people - a reduction of 6,088.
Forest begin their 2016-17 campaign at home to Burton Albion on 6 August.
The initial delay was because the council were not satisfied that a suitable person was found to fill the role as certificate holder - a legal requirement for sports clubs - but this issue has now been rectified.
"We are pleased that Nottingham Forest has now put forward a suitable person to take on the crucial role of safety certificate holder," said Nottinghamshire County Council's Robert Fisher.
"However, the council and our Safety Advisory Group partners need to be confident that the club is fully supporting the certificate holder to fulfil their role and unfortunately a number of concerns remain."
A statement from Forest said: "The club will continue to work in partnership with the council in order to address the outstanding issues to ensure that the safety factor is restored to full capacity as quickly as possible."
The Reds, who host Premier League Hull City in pre-season game on Saturday, had attendances higher than 24,357 three times last season - against Derby County in November (25,114), the visit of Leeds United in December (27,551) and the FA Cup fourth-round tie with Watford (24,703).
Fisher added: "We require evidence to demonstrate that safety matters are discussed in senior management meetings at the club.
"We also await an action plan for improvements to the facilities for visiting disabled spectators and an up-to-date written safety policy outlining roles at the club.
"As a consequence of this, a restriction on spectator capacity is required until these issues are resolved.
"The council is continuing to work closely with the club to see that an appropriate action plan is carried out to address remaining issues, so we are able to restore the club's previous full capacity status over the coming weeks."
Pub and restaurant group Mitchells & Butlers (M&B) has appointed the director of a rival company as its new chief executive.
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Nottingham Forest's capacity has been reduced by 20% by Nottinghamshire County Council to fewer than 25,000.