"regular race between two or more boats for prizes," 1650s, originally the name of a boat race among gondoliers held on the Grand Canal in Venice, from Italian (Venetian dialect) regatta, literally "contention for mastery," from rigattare "to compete, haggle, sell at retail," a word of uncertain origin. [Klein's sources, however, suggest a source in Italian riga "row, rank," from a Germanic source and related to English row (v.).]
The general meaning of "boat race, yacht race" is usually considered to have begun with a race on the Thames by that name June 23, 1775 (see OED), but there is evidence that the word was used in English as early as 1768.