Stephen White, who has been acting as interim chief executive officer, will leave YBS to take on a new role at Santander.
The society says both appointments are subject to regulatory approval.
YBS chairman John Heaps comments: “Alasdair Lenman has 23 years of experience in finance and has worked in financial services for 15 years, most recently as our chief finance officer.”
“He has played a leading role in the development of our existing strategy, which has yielded some of our strongest financial results in our history. The process to appoint the next permanent Chief Executive Officer is well advanced and will conclude as planned later this year,” Heaps adds.
Commenting on his appointment, Lenman says: “I look forward to supporting the Society until the process for appointing a permanent chief executive officer concludes.”