Gaius Marius died in 86BC

Marius had spent her entire life becoming embroiled in some sort of battle, and his later years were no different. Days after taking office for the seventh time, he started to lose focus and display symptoms of illness. Due to this, he passed away at the age of 70 just seventeen days after being elected. Gaius Marius's cause of death has been the subject of much conjecture, but the most widely accepted theory is that he acquired pleurisy and passed away as a result of it.

Gaius Piso recalls that Marius went on a stroll with his friends and told them about all of his accomplishments, adding that no wise man should allow himself to become wealthy. Later, an unnamed source cites Plutarch as saying that Marius started acting as he would on the battlefield after having a period in which he falsely believed he was in charge of the Mithridatic War. Last but not least, Plutarch recalls that once an ambitious man, Marius bemoaned in his hospital bed that he had not accomplished all that he could, despite having amassed a large great estate and been selected as consul more frequently than any other man before him.