In a ceremony at the Great Hall of the People in Beijing, Mr Xi raised his right fist and placed his left hand on a red leather book of the Chinese constitution as he was sworn in.
The most powerful leader since Mao Zedong pledged to “build a prosperous, strong, democratic, civilised, harmonious and great modern socialist country” as Chinese Communist Party (CCP) lawmakers broke into applause.
Mr Xi, who turns 70 this year, is the first ever head of state to serve more than 10 years since Communist China was founded in 1949.
His appointment in a ceremonial vote – he won by 2,952 to 0 – was a foregone conclusion as members of the National People’s Congress are appointed by the CCP whose top ranks have been filled with his allies.
First to congratulate Mr Xi were North Korean leader Kim Jong-un and Russian president Vladimir Putin, who said the third term was “acknowledgement of his achievements as the head of state”.
After the vote Mr Xi stood to a standing ovation from lawmakers and chatted with his top lieutenants Wang Huning, Zhao Leji, and Li Qiang, who is expected to be to be named premier on Saturday.
Mr Li is best known for ruthlessly enforcing a “zero-Covid” lockdown on Shanghai last spring as party boss of the Chinese financial hub, proving his loyalty to Mr Xi despite complaints from residents over their lack of access to food, medical care and basic services.
The parliament also appointed Zhao Leji as the new head of the National People’s Congress and appointed vice premier and party veteran Han Zheng as vice president.
In 2018, Mr Xi abolished two-term limits on the presidency, effectively allowing him to rule for life.
Mr Xi and those awarded other posts were believed to have run unopposed as no candidate lists were distributed. The election process remains almost entirely shrouded in secrecy, with the exception to the process by which delegates to the congress placed four ballots into boxes placed around the vast auditorium of the Great Hall of the People.
Mr Xi was also unanimously voted commander of the 2 million-strong People’s Liberation Army (PLA), a force that takes its orders from the party.
Since securing powerful posts as head of CCP and military leadership at the party congress in October, Mr Xi’s leadership has faced challenges of unprecedented mass protests over his zero-Covid policy and anger over the deaths of people after its abandonment.
The Chinese economy has also faced the brunt of three years of strict Covid restrictions and the waning confidence of investors.