Blair House, Presidential guest house complex on Pennsylvania Avenue, Washington, D.C., United States

Blair House, the President's Guest House, is a complex of four formerly separate 19th-century brick residences on Pennsylvania Avenue, diagonally across from the White House. Renovations between the 1950s and 1980s joined Blair House, Lee House, Peter Parker House and 704 Jackson Place into one building of about 70,000 square feet (6,500 m2), larger than the Executive Residence of the White House, with 14 guest bedrooms. The cream-painted central section has black shutters, a black metal balcony and a green awning.

Blair House was built in 1824 as a private home for Joseph Lovell, the eighth Surgeon General of the U.S. Army. Francis Preston Blair, a newspaper publisher and advisor to Andrew Jackson, bought it in 1836, and it stayed in his family for a century. From late 1948 to March 1952 it housed President Truman and his family during the White House reconstruction.

The name Blair House comes from Francis Preston Blair, the journalist and adviser to Andrew Jackson who bought the building in 1836; his family kept it for a century. His son Montgomery Blair, Lincoln's postmaster general, lived here, and on April 18, 1861, the elder Blair relayed Lincoln's offer to command the Union forces to Robert E. Lee in this house.

The United States Secret Service manages security during visits by foreign heads of state. The Diplomatic Security Service handles responsibility for other international delegations and official guests.

On November 1, 1950, Puerto Rican nationalists Griselio Torresola and Oscar Collazo attacked Blair House to kill President Truman, who was living there during the White House renovation. White House policeman Leslie Coffelt shot Torresola but was mortally wounded; the attempt failed.