The news came after the 68-year-old ended his final term in March.
Li served as China’s top economic official for a decade, The Associated Press reported.
He died at 12:10 am on Friday while resting in Shanghai, according to Chinese state news outlet CCTV.
Li was known as an economic reformer and advocate for private business, which put him at odds with Chinese President Xi Jinping.
The former premiere was left with little power after Xi tightened his control over the Chinese economy.
After Li’s term ended, Xi stayed on for an unprecedented third term and installed loyalist Li Qiang as the new premiere.
The replacement later told reporters it was his job to do whatever Xi said.
When Li began his term in 2013, many believed he would succeed former Communist Party leader Hu Jintao.
But he was passed over for Xi, who rolled back Hu’s consensus-based leadership style and consolidated power.
Li was axed from the party’s Standing Committee in October, two years before the mandatory retirement age of 70.
Xi awarded himself an third five-year term on the same day.
This was unprecedented, as all past Chinese presidents have stepped down after a decade.