The longtime head of Northwell Health is stepping aside after more than 20 years running New York’s largest health system.

Michael Dowling, who has served as president and CEO since 2002, will officially step down in October and be replaced by longtime Northwell executive John D’Angelo.

“It has been an extraordinary privilege to lead Northwell through a period of unprecedented growth and clinical transformation that has enabled our team members to make a meaningful difference and improve the lives of the tens of millions of patients and families who we’ve cared for over the last 25 years,” Dowling said in a statement.

Dowling will transition into a CEO emeritus role, advising on public health issues and continuing work in education and policy.ending a transformational run that turned a small network of Long Island hospitals into one of the health care systems in the nation.

Under Dowling’s leadership, Northwell eventually grew to a network of a thousand facilities and 28 hospitals across New York and Connecticut — with over 100,000 employees and more than 14,000 affiliated physicians.

In 2022, he was named the most influential person in health care by Modern Healthcare after he launched a national initiative to address gun violence as a public health issue, bringing together more than 60 health care CEOs to back prevention efforts and legislation.

Dowling also oversaw major investments in research and education, expanded medical training programs, and helped Northwell become a national leader in bioelectronic medicine.

The system’s board voted unanimously to appoint D’Angelo CEO, calling him the right person to lead Northwell into its next chapter.

He began his 25-year tenure as an ER physician in Glen Cove before eventually rising to lead part of its health system.

Dowling said D’Angelo’s is a “tremendous leader who will lead Northwell to greater heights,” and believes he will “raise the bar on the quality of care” offered throughout the state.

“Health care is a calling. Every minute of every day, we have an opportunity to change someone’s life for the better,” D’Angelo said in a statement.

“I look forward to leading our more than 100,000 team members who contribute to this critically important mission — advancing better health for all.”