Gustaf Fredrik Rydberg (born September 13, 1835, in Malmö; died October 11, 1933, in the same place) was a Swedish landscape painter of the Düsseldorf School. Rydberg was born as the son of the postmaster Gustaf Isak Rydberg and his wife Elise Charlotte Zickerman. In his hometown Malmö, he attended the Latin School for four years.

From 1852 to 1855, Rydberg studied at the Royal Danish Academy of Fine Arts in Copenhagen, where he was a student of the landscape painter Frederik Christian Jakobsen Kiærskou (1805–1891). He then attended the Royal Swedish Academy of Fine Arts in Stockholm from 1857 to 1859 under Johan Edvard Bergh.

Like many other Swedish painters of his time, Rydberg went to the Düsseldorf Art Academy in 1859. There, he was a student of Hans Fredrik Gude until 1862 and was taught by Oswald Achenbach in the academic year 1862/1863. After his studies, Rydberg stayed in Düsseldorf for a while but traveled to Scania, his homeland in southern Sweden, during the summers to paint landscapes. In 1864, he settled in Stockholm.

In 1868, he accompanied Charles XV of Sweden and Norway on a trip to Norway. The following year, the king financed another trip for him to Norway. In 1870, he returned to Düsseldorf. Around 1885, he moved to Torsebro, a place near Kristianstad. On March 14, 1887, he married Ebba Josephina Borgström (1839–1905) in Kristianstad.

Rydberg was friends with the painter Alfred Wahlberg, whom he had met in Düsseldorf, the painter Reinhold Norstedt, and the art historian Axel Gauffin (1877–1964). In 1920, the Royal Swedish Academy of Fine Arts organized a jubilee exhibition featuring around 260 of his works. Rydberg's grave is located in the Old Cemetery of Malmö.

Gustaf Rydberg is regarded as one of the outstanding landscape painters of Sweden in the 19th century, masterfully capturing the beauty and tranquility of the Scandinavian nature.