The Virginius Affair (sometimes called the Virginius Incident) was a diplomatic dispute that occurred in the 1870s between the United States, the United Kingdom and Spain, then proprietor of Cuba.

The Virginius was a blockade-runner used in the American Civil War; it became a prize of the United States federal government, by which it was sold in 1870 to an American, J. F. Patterson , who immediately registered it in the New York Custom House . It later appeared that Patterson was merely acting for a number of Cuban insurgents who falsely flew the American flag and were using the Virginius to deliver contraband to the Cubans fighting the Ten Years War.

On October 31, 1873 then commanded by Joseph Fry , a former officer of both the Federal and Confederate navies, and having a crew of 52 (chiefly Americans and Englishmen) and 103 passengers (mostly Cubans), she was captured off Morant Bay , Jamaica, by the Spanish vessel Tornado, and was taken to Santiago de Cuba, where, after a summary court-martial, 53 of the crew and passengers, including Fry and some Americans and Englishmen, were executed on November 4, 7 and 8 as pirates. The intervention of the HMS Niobe prevented further deaths.

Relations between Spain and the United States became strained, and war seemed imminent; but on the December 8 the Spanish government agreed to surrender the Virginius to the U.S. on December 16, to deliver the survivors of the crew and passengers to an American warship at Santiago, and to salute the American flag at Santiago on the December 25 if it should not be proved before that date that the Virginius was not entitled to sail under American colors.

The Virginius foundered off Cape Hatteras as she was being brought to the United States. The Attorney-General of the United States decided before December 25 that the Virginius was the property of General Quesada and other Cubans, and had had no right to carry the American flag.

Under an agreement of the February 27, 1875, the Spanish government paid to the United States an indemnity of $80,000 for the execution of the Americans, and an indemnity was also paid to the British government.