America's prestigious Harvard University, founded by Puritan settlers almost 400 years ago, has a new chief chaplain - and he doesn't believe in God.

Greg Epstein, 44, took up the role this week, becoming the first atheist elected president of Harvard's organization of chaplains.

"I'm obliged and honored," he wrote on Twitter.

Mr Epstein has been Harvard's humanist chaplain since 2005 and is the author of the bestselling book "Good Without God: What a Billion Nonreligious People Do Believe".

He will lead a group of more than 40 chaplains who represent some twenty different religions and beliefs including Christianity, Judaism, Hinduism and Buddhism.

His appointment comes as young people in the United States increasingly identify as spiritual but without a religious affiliation.

"There is a rising group of people who no longer identify with any religious tradition but still experience a real need for conversation and support around what it means to be a good human and live an ethical life," Mr Epstein told The New York Times.

"We don't look to a god for answers. We are each other's answers," he added.

Mr Epstein did not immediately respond to request for comment from AFP.

A 2019 Pew Research Center study found that the United States remains a predominantly Christian country, with 43% identifying as Protestant and 20% as Catholic.

But more than a quarter of those surveyed (26%) described their religious identity as atheist, agnostic or "nothing in particular," up from 17% in 2009.

Mr Epstein, born into a Jewish family in New York, has also been the humanist chaplain at the Massachusetts Institute of Technology (MIT), another major university in the Boston area, since 2018.

Harvard, founded in 1636 to train the Protestant clergy, is the oldest institution of higher education in the United States.