John V. Kelleher, a vivid storyteller with a mischievous sense of humor whose work at Harvard defined the field of Irish studies in America, died Jan. 1 of pneumonia. He was 87.

Kelleher, an emeritus professor of Irish Studies in the Department of Celtic Languages and Literatures, first came to Harvard in 1940.

One of the world’s foremost Irish scholars, he specialized in modern Irish literature and the history of the early Irish annals, a project he once said would take him “25 lifetimes” to complete.

Kelleher was also a fluent Irish speaker who could stump native Dubliners with his knowledge of their language.

“He prided himself on speaking Irish. And he brought back wonderful stories about speaking Irish in Ireland,” recalled William H. Bossert ’59, Arnold professor of science and a former co-master of Lowell House, where Kelleher served as a member of the Senior Common Room.

“It turns out that many people in Ireland don’t really speak Irish, so he was always calling people’s bluffs,” Bossert said.

Growing up in a heavily Irish neighborhood in Lawrence, Mass., Kelleher developed an early interest in Irish studies. His grandmother, an immigrant herself, began to teach him Irish as a child.

After graduating from Dartmouth in 1939 with a degree in English, Kelleher came to Harvard as a member of the Society of Fellows, and during World War II served briefly in the Pentagon.

But it was on a bicycle trip through Ireland after the war that he forged friendships with some of the great modern Irish writers, including Frank O’Connor and Seán Ó Faoláin.

From 1947 to 1986, Kelleher taught as a professor in the English and history departments as well as the Department of Celtic Literature and Languages.

Colleagues remember Kelleher as a “giant in the field” who informed a generation of other Irish scholars.

“Just about everyone working in the field of Celtic studies—and especially in Irish studies—was either a student of his or was greatly influenced by his work,” said Robinson Professor of Celtic Languages and Literatures Patrick K. Ford.

Ford, who studied under Kelleher and now chairs the Department of Celtic Languages and Literatures, said Kelleher’s loss would be felt across the globe.

“He was a wonderful colleague, a great scholar, and has left students all over this country and all over the world as well,” Ford said.

But friends and family described Kelleher as a warm man who relished telling stories as much as he loved his academic work.