Li was nominated by Xi and appointed to the position at Saturday morning's session of the National People's Congress, China's ceremonial parliament.Â
That came a day after Xi, 69, secured a third five-year term as state leader, setting him up to possibly rule for life.
Li is best known for having enforced a brutal "zero-COVID" lockdown in Shanghai last spring as party boss of the Chinese financial hub, proving his loyalty to Xi in the face of complaints from residents over their lack of access to food, medical care and basic services.
Li, 63, came to know Xi during the future president's term as head of Li's native Zhejiang, a relatively wealthy southeastern province now known as a technology and manufacturing powerhouse.
Prior to the pandemic, Li built up a reputation in Shanghai and Zhejiang before that, as friendly to private industry, even as Xi enforced tighter political controls and anti-COVID curbs, as well as more control over e-commerce and other tech companies.
As premier, Li will be charged with reviving a sluggish economy still emerging from the COVID-19 pandemic and confronted with weak global demand for exports, lingering US tariff hikes, a shrinking workforce and an aging population.
He takes on the job as authority of the premier and the State Council, China's Cabinet, has been steadily eroding as Xi shifts more powers to bodies directly under the ruling Communist Party.
At the opening of the annual congress session on Sunday, outgoing Premier Li Keqiang announced plans for a consumer-led revival of the struggling economy, setting this year's growth target at "around 5 per cent." Last year's growth fell to 3 per cent, the second-weakest level since at least the 1970s.
As with Xi's appointment on Friday, there was no indication that members of the NPC had any option other than to endorse Li and other officials picked by the Communist Party to fill other posts.
Unlike Xi, who received the body's full endorsement, Li's tally included three opposed and eight abstentions.
Xi's new term and the appointment of loyalists to top posts underscore his near-total monopoly on Chinese political power, eliminating any potential opposition to his hyper-nationalistic agenda of building China into the top political, military and economic rival to the US and the chief authoritarian challenge to the Washington-led democratic world order.