Gustav Antonio Gjessing (22 September 1835 – 3 December 1921) was a Norwegian philologist.
He was born in Drammen as a son of Christian Gjessing and Anne Thrane Stoltenberg.
In July 1865 in Kristiania he married Helga Margrethe Elisabeth Monrad (1845–1920), a daughter of the famous philosopher Marcus Jacob Monrad.
He was the father of archeologist Helge Gjessing, an uncle of ophthalmologist Harald Gjessing and grandfather of archaeologist Gutorm Gjessing.He enrolled as a student in 1854, and graduated with the cand.philol.
degree in 1861.
He worked as a school teacher from 1862, from 1865 at Kristiansand Cathedral School.
He then worked at a school in Arendal from 1880 to his 1904 retirement.
His specialty was the Old Norse language, and he published a number of academic works during his teacher career.
His main work was Undersøgelse af Kongesagaens Fremvæxt, published in two volumes in 1873 and 1876.
In 1899 he published a translation of the Poetic Edda.
He was also a member of Arendal city council from 1897 to 1900, and was a chairman of the local library and museum.
After retiring he moved to Lysaker with his wife, where he died in December 1921.