Mr Kim, however, avoided direct criticism of Washington during the event, which took place less than four weeks before the US presidential election.
Instead, he focused on a domestic message urging his people to remain firm in face of "tremendous challenges" posed by the coronavirus pandemic and crippling US-led sanctions over his nuclear programme.
Outside observers were expecting the North to possibly unveil the latest weapons in its growing nuclear arsenal that threatens US allies in Asia and the American mainland.
South Korea's Joint Chiefs of Staff said early in the day that there were signs that the North had mobilised "large crowds and equipment" for a military parade at Pyongyang's Kim Il Sung Square during the early morning hours.
In the evening, North Korean state television began airing a taped broadcast of the event, which began late on Friday.
Goose-stepping troops were seen marching in the streets in front of the brightly illuminated square, as a military band performed while moving in formation, shaping the numbers "10.10," "1945," and "2020", as well as a hammer and sickle - symbols of the ruling Workers' Party.
The performers and tens of thousands of spectators roared as Kim, dressed in a grey suit and tie, appeared from a building as the clock struck midnight.
Mr Kim, flanked with senior officials and smiling widely, waved to the crowd and kissed children who presented him with flowers before taking his spot on the podium.
During his speech, Mr Kim repeatedly thanked his "great people" for overcoming "unexpected" burdens and thoroughly abiding by the anti-virus measures imposed by the ruling party and government to keep the country Covid-19-free, a claim that has been widely questioned by outside observers.
He also extended an olive branch to rival South Korea, expressing hope that the countries could repair bilateral ties once the threat of the pandemic is over.
Earlier on Saturday, masked citizens lined up to lay flowers at the statues of Kim Il Sung and Kim Jong Il, the father of the current ruler, at Pyongyang's Mansu Hill.
A huge street poster highlighted the ruling Workers' Party's symbol – a hammer, brush and sickle – with letters that read "Best glory to our great party".
The North's official Korean Central News Agency (KCNA) said residents in Kaesong and other regions who had lost their homes to recent natural disasters marked the party anniversary by moving into newly built houses and that they praised Kim Jong Un for looking after them as "their father".
KCNA also reported that Chinese president Xi Jinping sent a letter to Mr Kim saying that Beijing would continue to "defend, consolidate and develop" bilateral relations with Pyongyang.
This year's anniversary comes amid deadlocked nuclear negotiations with the Trump administration and deepening economic woes that analysts say are shaping up as one of the biggest tests of Mr Kim's leadership since he took power in 2011.
South Korean officials and analysts have said North Korea could showcase a new intercontinental ballistic missile or other nuclear-capable weapons during a parade, which would highlight how the country has continued to expand its military capabilities amid stalled nuclear talks.
Expressing deep frustrations over the diplomacy, Mr Kim pledged in December to soon unveil a "new strategic weapon to the world" while declaring to bolster his nuclear deterrent in face of "gangster-like" US pressure.
Many analysts believe North Korea will avoid serious negotiations or provocations before the US presidential election in November, as a change in US administrations could force the country to recalibrate its approach toward Washington and Seoul.