Wilson was appointed CEO in 2012 after joining at group chief financial officer in 2009.
Sir Nigel has agreed to continue as chief executive until a new CEO starts and will support a smooth transition following the appointment, the company said.
"It is envisaged that this process will take around a year," a company sattement said. "In the meantime, Sir Nigel will continue to focus on delivering the current strategy of the group, supported by the executive team."
L&G also said that its guidance on full-year operating profit for last year remains unchanged and that it expects an operational surplus of 1.8 billion pounds ($2.23 billion).
($1 = 0.8071 pounds)
(Reporting by Huw Jones; Editing by Ed Osmond and David Goodman)
