Years of shrinking interest rates, demographic challenges and threats from rapidly advancing technology are finally coming to a head at Japan's biggest banks as they prepare to eliminate thousands of positions and downsize branches.

Mizuho Financial Group Inc. is considering cutting as many as 19,000 jobs — about a third of its workforce — mainly through attrition over the next 10 years, according to people with knowledge of the matter. Mitsubishi UFJ Financial Group Inc. is considering shrinking its workforce by about 10,000 over a decade, Chief Executive Officer Nobuyuki Hirano has said. Sumitomo Mitsui Financial Group Inc. plans to "streamline" 4,000 positions over three years by digitizing branches and making processes more efficient.

The CEOs of the three Tokyo-based banks may expound on their cost-cutting plans next week when they brief on fiscal second-quarter results. Their profits probably fell in the period, according to analysts surveyed by Bloomberg, underscoring the challenges they face as negative interest rates cut into lending income and a push overseas adds to their costs.