The Spanish lender has seen its shares soar in value this year, propelling it to a market capitalization of €91 billion ($104 billion). Meanwhile, UBS shares have tumbled as the bank faces the possibility of dramatically higher capital requirements in Switzerland, shrinking its valuation to €86 billion. 

Britain’s HSBC Plc remains as Europe’s biggest bank with a market value of £139 billion ($184 billion.) 

While Santander shares have taken a hit in recent weeks, the stock is still up more 30% this year, riding a wave of investor optimism about the health of European banks and the potential for more massive public spending in the region. In February, the bank announced record profit and plans to buy back €10 billion of its shares over the coming years.

Banks remain as Europe’s best sector since the start of the year. The Stoxx 600 Banks Index has rallied 15%, while the broader benchmark is flat. Lenders on the continent will kick off earnings season next week, with investors focused on the economic hit from the US trade war.