Policymakers have long said Europe's ailing banking sector needs to consolidate, but regulatory and political obstacles have hindered big deals over the past decade.
This year, however, has seen major domestic bank tie-ups in Italy and Spain, with bankers saying regulators are now more willing to wave deals through.
"Already since late (2019), and since COVID, things are crystal clear," UBS Chief Executive Sergio Ermotti told an annual Bank of America Merrill Lynch conference.
"The train left the station in that sense, and consolidation is inevitable," Ermotti said, adding that Europe faced the risk of its banks becoming too small to survive or compete.
Deutsche Bank's chief financial officer James von Moltke said it supported the "appropriate or valid industrial logic" of mergers among the region's larger banks.
"We've been very focused on executing on our own strategy, and we think that strategy would prepare us to engage in merger activity when the time comes and the right opportunities arise," von Moltke said at the same "virtual" financials conference.
"So we are expecting this wave but we are also working hard to prepare on our side," he said.
There has been growing speculation about a potential deal in Switzerland, heightened last week when the board of UBS, which last year held brief tie-up talks with Deutsche Bank, gathered to discuss strategy.
UBS recently examined a potential deal with Credit Suisse, whose executives also expect consolidation.
Ermotti, who is due to be replaced at UBS by former ING head Ralph Hamers in November, declined comment on any role the Swiss bank might play in the consolidation.
Mergers would be positive for the industry, so long as tie-ups were complementary, he added.
Only last year Deutsche Bank called off merger talks with domestic rival Commerzbank and von Moltke said domestic mergers "frankly present some challenges".
Raimund Roeseler, who oversees banking supervision at German financial regulator BaFin, said mergers could be helpful, but were not always the solution.
"Do we really believe that the problems of the German banking market would be solved if we only had 700 or 500 banks instead of 1,400? I don't think so," he told another banking conference.
By Tom Sims and Brenna Hughes Neghaiwi