NEW YORK — Hunter Harrison, the president and chief executive of railroad giant CSX, has died, the company announced Saturday. He was 73.

CSX confirmed Mr. Harrison’s death in a statement, saying it was caused by ‘‘unexpectedly severe complications’’ from a recent illness. His death comes only a couple days after the company announced he was taking an unplanned medical leave of absence.

Born in Memphis, Tenn., Harrison was a longtime railroad executive who made his career turning around railroads. Before joining CSX in March, Mr. Harrison was president and chief executive of Canadian Pacific Railway Ltd. and the Canadian National Railway Company. He also was the head of the Illinois Central Railway in the 1990s.

‘‘Hunter was a larger-than-life figure who brought his remarkable passion, experience and energy in railroading to CSX,’’ the company said in a statement.

He was hired by Florida-based CSX in March under shareholder pressure. But recently there had been concerns about his health. The Wall Street Journal reported in May that Mr. Harrison often worked from home and occasionally required portable oxygen.

CSX shares fell sharply Thursday when the company announced Mr. Harrison was taking a leave.

Edward Kelly, chairman of CSX’s board of directors, said Jim Foote, who was named acting chief executive when Mr. Harrison took the leave of absence, will continue in his role as acting chief executive. Kelly called Mr. Harrison’s death ‘‘a major loss’’ to the company but said they would try to implement some of the ideas Mr. Harrison had for the railroad before his death.