General Electric Co. named health-care head John Flannery its new chairman and chief executive officer, ending Jeffrey Immelt’s 16-year tenure that included a withdrawal from financial services and a renewed focus on energy-related businesses. Flannery will become CEO on Aug. 1., and will add the title of chairman on Jan. 1, the Boston-based company said in a statement Monday. The appointment is the result of succession planning that’s been under way since 2011, the company said.

The CEO-designate “has led complex financial and industrial businesses all over the world, including running GE Healthcare, GE in India and the business development team for GE through the successful acquisition of Alstom,” said Jack Brennan, the company’s lead independent director. “John has had a direct influence on the company’s direction, its financial health and its position as the world’s premier digital industrial company.”

Immelt had been under pressure amid a slide in GE’s stock to the lowest level in a year and a half. The shares have fallen 12 percent this year, compared with an 8.6 percent gain for the Standard & Poor’s 500 Index. GE shares rose 3.1 percent to $28.80 before regular trading in New York.