| Socialist Left | |
| Native Name: | Izquierda Socialista |
| Abbreviation: | IS |
| Foundation: | [1] |
| Youth Wing: | Juventud de Izquierda Socialista |
| Womens Wing: | Isadora |
| National: | Workers' Left Front[2] |
| Split: | MST |
| International: | International Workers' Unity – Fourth International[3] |
| Ideology: | Trotskyism |
| Position: | Far-left |
| Membership Year: | 2017 |
| Membership: | 30,523[4] [5] |
| Newspaper: | El Socialista |
| Headquarters: | Buenos Aires, Argentina |
| Seats1 Title: | Seats in the Chamber of Deputies |
| Seats2 Title: | Seats in the Senate |
| Colours: | Red |
| Website: | izquierdasocialista.org.ar |
| Country: | Argentina |
Socialist Left (Spanish; Castilian: Izquierda Socialista; IS), officially registered as the Left for a Socialist Option (Izquierda por una Opción Socialista), is a Trotskyist political party in Argentina. It was founded in 2006 as a split from the Socialist Workers' Movement. It is the Argentine section of International Workers' Unity – Fourth International. It is one of three parties that make up the Workers' Left Front.
Members include Liliana Olivero, a former deputy in the provincial legislature in Córdoba Province, Argentina, Angélica Lagunas, a provincial deputy in Neuquén Province, Mercedes de Mendieta, a deputy in the Autonomous City of Buenos Aires, and Graciela Calderón, a deputy in Buenos Aires Province.