No. Societies that were socialist to varying degrees have existed or been imagined (in the form of utopias) since ancient times. Examples of actual socialist societies that predated or were uninfluenced by Karl Marx were Christian monastic communities during and after the Roman Empire and Robert Owen’s utopian social experiments in the 19th century. Premodern or non-Marxist works envisioning ideal socialist societies include Plato’s Republic, Thomas More’s Utopia, and Charles Fourier’s Social Destiny of Man.