william lewis dayton (february 17, 1807 – december 1, 1864) was an american politician, active first in the whig party and later in the republican party. in the 1856 presidential election, he became the first republican vice-presidential nominee when nominated alongside john c. frémont. the republican party lost that campaign. during the american civil war, dayton served as the united states ambassador to france, a position in which he worked to prevent french recognition of the confederacy.