Sydir Tverdokhlib – Ukrainian poet, translator and politician.

Sydir Vorobkevych (1836–1903) was a Ukrainian composer, writer, Eastern Orthodox priest, teacher, artist, and newspaper editor of Bukovina. He used following pen-names: Danylo Mlaka, Demko Makoviychuk, Morozenko, Semen Khrin, Isydor Vorobkevych, S.Volokh, and others.

Sydney Finkelstein is the Steven Roth Professor of Management and faculty director of the Tuck Executive Program (TEP) at the Tuck School of Business at Dartmouth College. He is also the faculty director of the Center for Leadership at Tuck. His specialty is business leadership and strategy.

Sydney George Fisher was a United States lawyer and historian, and is best known for his work The True History of the American Revolution.

Sydney Grundy was an English dramatist. Most of his works were adaptations of European plays, and many became successful enough to tour throughout the English-speaking world. He is, however, perhaps best remembered today as the librettist of several comic operas, notably Haddon Hall.

Sydney Omarr was an American astrologer and an astrology consultant to the rich and famous. His daily Sun Sign Horoscope column appeared in more than 200 newspapers and his annual forecast books for each sign of the zodiac sold over 50 million copies.

Sydney Rosenfeld (1855–1931) was an American playwright who wrote numerous plays, and adapted many foreign plays. Close to fifty of his creations played on Broadway.

Sydney Smith was an English wit, writer, and Anglican cleric. Besides his energetic parochial work, he was known for his writing and philosophy, founding the Edinburgh Review, lecturing at the Royal Institution and remembered for his rhyming recipe for salad dressing.

Sydney Taylor was an American writer, known for her series of children's books about a Jewish-American family in New York during the early 20th century. Her first book won the Charles W. Follett Award in children's literature.

Sydney Thompson Dobell was an English poet and critic, and a member of the so-called Spasmodic school.