William Howard Taft first did it on April 14, 1910. This will be the 48th time a president has made an opening-day pitch in the nation's capital.
The Nationals open at home on April 5 against the Philadelphia Phillies.
"I am proud that President Obama will continue the long presidential tradition of throwing out the first pitch of opening day in Washington, D.C.," baseball commissioner Bud Selig said.
Obama will have an experienced target, too: When he played in Texas, new Nationals catcher Ivan Rodriguez, a 14-time All-Star, twice caught ceremonial pitches from President George W. Bush, a former Rangers owner.
Rodriguez is looking forward to this occasion.
"He's a great guy, a great president, a sports fan," Rodriguez said. "It's going to be a great day."
This will be the first time President Obama attends a game at Nationals Park.
Pitcher John Lannan will be starting the game for the Nationals and worried he could be warming up in the bullpen right when the Commander in Chief is touring the home clubhouse.
"We were hoping he'd do it last year. The timing's right," Lannan said. "You have some perks when you're living in D.C."
Obama threw out the first pitch at last year's All-Star game in St. Louis, wearing a White Sox jacket. Noting that the Nationals host the White Sox this season for a three-game series June 18-20, Washington manager Jim Riggleman joked, "He's going to be answering some tough questions about whether he's a Nationals fan or a White Sox fan."
