Deutsche Bank AG moved Sunday to gut its global ambitions as a trading powerhouse, cutting 18,000 jobs and retreating to its German banking roots in a radical overhaul to try to save itself after years of decline.

Deutsche Bank’s restructuring plan reorders the bank’s executive ranks under Chief Executive Christian Sewing, with several senior officials leaving and business lines redrawn for the third time in four years.

The moves are a dramatic capitulation 20 years after Deutsche Bank acquired Bankers Trust in the U.S., enabling a rising profile in bond trading and other areas that helped it compete with Goldman Sachs Group Inc. and other big U.S. investment banks on the global stage.

“What we have announced today is nothing less than a fundamental rebuilding of Deutsche Bank,” Mr. Sewing wrote in a message to staff, adding that the changes “will bring us closer to our core strength, our DNA.”

The German lender’s struggles have been symptomatic of a broader malaise among Europe’s investment banks. Struggling with low interest rates and political uncertainty, Europeans are dominated by U.S. rivals on their home turf.