Sveinn Kristjan Bjarnarsson (January 13, 1887 – July 8, 1960), also known as Edgar Holger Cahill, was an Icelandic-American curator, writer and arts administrator.

After two difficult years with the Icelandic farmers, Cahill ran away at first to neighboring farms where he found work and eventually to Winnipeg, in search of distant cousins.

Cahill's employment in the field of visual arts began in 1921 when he was hired by John Cotton Dana at the Newark Museum and the Society of Independent Artists to write publicity about their activities.

While at Newark, he also published fiction, essays and short stories including art criticism for the magazines Shadowland International Studio and the New York Herald Tribune.

He published a novel, Profane Earth in 1927 and, in 1930, "A Yankee Adventurer" a biography of Frederick Townsend Ward and his role in the Taiping Rebellion of 1861.

Under his leadership community art centers were established in over 100 towns and cities nationwide, murals drawing upon the geographical environment were painted in public buildings throughout the country, and some 10,000 artists and craft workers were sustained through the Great Depression.

The following year, he took a leave of absence from the WPA to stay in New York City and direct a large survey exhibition at the 1939 World’s Fair, American Art Today.

Hampered by various illnesses after his busy tenure as Director of the Federal Art Project and a severe heart attack in 1947, he managed to complete two novels, Look South to the Polar Star, in 1947, and The Shadow of My Hand, in 1956, set in the Midwest of his youth.

In the same year he began studying poetry with Stanley Kunitz, and taped a memoir for the Columbia University Oral History Project.