Klaus Wagenbach was a German author and publisher who was the founder of publisher Verlag Klaus Wagenbach.

Klaus Zimmermann is a German ancient historian.

Klavdiya Ivanovna Shulzhenko was a Soviet popular female singer and actress.

Klāvs Elsbergs was a Latvian poet and translator. He was the son of Latvian poet Vizma Belševica.

Kléber Haedens, was a French novelist and journalist. He was a monarchist and a member of the Action Française in the 1930s. During World War II he worked as a secretary for Charles Maurras. He was a friend of Antoine Blondin, Michel Déon and Roger Nimier, and closely linked to the Hussards movement in post-war France. He received the Prix Interallié in 1966 for L'été finit sous les tilleuls and the Grand Prix du roman de l'Académie française in 1974 for Adios.

Klemens Janicki (1516–1543) was one of the most outstanding Latin poets of the 16th century.

Klementyna Hoffmanowa, born Klementyna Tańska was a Polish novelist, playwright, editor, translator, teacher and activist. She was the first woman in Poland to support herself from writing and teaching, as well as one of Poland's first writers of children's literature.

Klim Zhukov is a Russian author, vlogger, and historical reenactor. He is a medievalist historian and science fiction author. He is also involved in historical reenactment. He is a bestselling author. In a survey conducted in 2019, he entered the top 10 trust rating in the Russian Internet. He collaborates with Dmitry Puchkov.

Klim(ent) Smoliatich was the Metropolitan of Kiev and All-Rus' from 1147 to 1154.

Kliment Arkadievich Timiryazev was a Russian Imperial botanist and physiologist and a major proponent of the Evolution Theory of Charles Darwin in Russia. He founded a faculty of vegetable physiology and a laboratory at the Petrovskoye Academy.