Rudolf Frentz was a Russian painter of German origin, the father of the artist Rudolf Rudolfovich Frentz.
Born in 1831 in Berlin, in 1854 Rudolf Frentz graduated from the Berlin Academy of Arts. In 1857, he moved to St. Petersburg, where he painted portraits on commissions. Among his works are the portraits of the Grand Dukes Nikolai Nikolaevich and Vladimir Aleksandrovich, other members of the Russian imperial family. He was also known as an animalist painter. In 1885, he was elected an honorary member of the Imperial Academy of Arts.