Ewen Stevenson, 47, takes on the key role following the abrupt resignation of predecessor Nathan Bostock - who announced in December that he was to quit just two months after starting the job.
Mr Stevenson will start on May 19, with Mr Bostock due to become deputy chief executive to Ana Botin at Santander UK.
Mr Stevenson has been handed the daunting task of overseeing a balance sheet crippled by £46 billion of losses over the past six years, at a business that is 80% owned by the taxpayer.
He joins after 25 years at Credit Suisse, where he rose to become co-head of investment banking for Europe, the Middle East and Africa, and advised the Treasury on its bail-outs of RBS and Lloyds Banking Group at the height of the financial crisis.
Mr Stevenson also advised on the restructuring of Northern Rock into a good bank and bad bank.