Who started jainism

Jainism is an ancient Indian religion that does not attribute its origin to a single founder. According to Jain tradition, it is eternal (Sanatan) and has been revealed in every time cycle by a series of enlightened teachers known as Tirthankaras. The first Tirthankara of the current time cycle is Rishabhanatha (Adinath), and the 24th and last Tirthankara of this era is Lord Mahavira (599–527 BCE), who revitalized and organized the Jain community and teachings.

Therefore, Jainism was not "started" by an individual, but Mahavira is often regarded as a key reformer and propagator of Jainism in historical times.