NEW YORK (AP) — Fidelity Investments named Abigail Johnson chief executive of the financial services company, the third CEO of the company founded by her grandfather.

Johnson, 52, is replacing her father, 84-year-old Edward Johnson, who has been CEO of Fidelity since 1977. He will stay on as chairman of the company's board.

The changes were announced Monday in a memo to Fidelity shareholders.

Fidelity in one of the world's biggest investors, managing 401(k)s and other retirement and investment accounts for 23 million people, according to the company's website. Its 401(k) plans are used by 193 of Fortune 500 companies. At the end of last year, it was managing 566 mutual funds. The company has $2 trillion assets under management.

Abigail Johnson has worked at the Boston company since 1988, starting out as a stock analyst. Most recently she was president of Fidelity's retail, workplace and institutional businesses. She is among the nation's wealthiest women, worth an estimated $12.3 billion, according to Forbes.

Johnson takes over Fidelity at a challenging time for the fund giant. Investors are increasingly turning to low-cost index funds, a specialty of rival Vanguard Group. And Fidelity has been playing catch-up in another low-cost option popular with investors, exchange-traded funds, which can be bought and sold during the day.