321 Florentina is an S-type (stony) main belt asteroid with a diameter of 28 km. It was discovered by Johann Palisa on 15 October 1891 in Vienna. He named the asteroid for his daughter, Florentine. Between 1874 and 1923, Palisa discovered a total of 122 asteroids. This asteroid is a dynamic member of the Koronis family. It is orbiting the Sun at a distance of 2.887 AU with an eccentricity (ovalness) of 0.046 and an orbital period of 1791.3 days. The orbital plane is inclined at an angle of 2.59° to the plane of the ecliptic. Photometric data collected during the asteroid opposition of 2011 was used to construct a light curve that displayed a rotation period of 2.87 hours. This is consistent with previous rotation estimates. A group of astronomers, including Lucy d'Escoffier Crespo da Silva, contributed data toward the discovery of spin-vector alignments in the Koronis family, which includes (321) Florentina. This was based on observations made between 1998 through 2000. The collaborative work resulted in the creation of 61 new individual rotation lightcurves to augment previous published observations.