John Patrick Parnell "Patsy" Cahill (April 4, 1865 – October 31, 1901) was a Major League Baseball outfielder. In addition to playing the outfield, Cahill played third base and shortstop and pitched 10 games. There is speculation that Cahill was the inspiration for Ernest Lawrence Thayer's poem "Casey at the Bat" after Thayer reportedly saw Cahill play in Stockton, California.