Ionescu (Francisized as Ionesco or Jonesco) is a Romanian surname, derived from the male given name Ion. It may refer to:

• Alexandru Ionescu, bobsledder
• Alexandru Ionescu, socialist militant
• Cassius Ionescu-Tulcea, mathematician
• Claudiu Eugen Ionescu, handball player
• Constantin Al. Ionescu-Caion, journalist
• Constantin Ionescu, chess grandmaster
• Corneliu Ionescu, painter
• Cristian Ionescu, politician
• Eduard Ionescu, Romanian table tennis player
• Elisabeta Ionescu, Romanian handball player
• Emanoil Ionescu, soldier
• Eugen Ionescu, also Eugène Ionesco, absurdist playwright
• Gheorghe Ionescu, painter
• Gheorghe Ionescu-Sisești, agronomist
• Ilarion Ionescu-Galați, violinist and conductor
• Ion Ionescu de la Brad, agronomist and economist
• Marian Ionescu, pioneer cardiac surgeon
• Mircea Ionescu Quintus, politician
• Nae Ionescu, philosopher
• Nicolae Ionescu, politician
• Ovidiu Ionescu, Romanian table tennis player
• Raicu Ionescu-Rion, socialist journalist, sociologist and art critic
• Sabrina Ionescu, American basketball player
• Șerban Ionescu, actor
• Silviu Ionescu, Romanian diplomat
• Ștefan Ionescu, ice hockey player
• Take Ionescu, politician
• Theodor V. Ionescu, physicist
• Valentin Ionescu, politician
• Valeriu Ionescu, writer, published under the name I. Valerian
• Vali Ionescu, long jumper

• Carmen Ionesco, Canadian discus thrower of Romanian descent
• Eugène Ionesco, playwright
• Eva Ionesco, actress
• Irina Ionesco, photographer
• Nicole Jonesco [fr] (1923–2008), French actress

• Sanda Movilă (born Maria Ionescu), novelist
• N. Porsenna (born Nicu Porsena Ionescu), writer and politician
• Urmuz (born Dimitrie Dim. Ionescu-Buzeu), writer