Tokyo's Nikkei 225 jumped 4.7% on Monday after Prime Minister Sanae Takaichi's governing party secured a two-thirds supermajority in a parliamentary election.
Takaichi is expected to pursue market-friendly policies, telling public broadcaster NHK that she aims to make Japan strong and prosperous.
Markets across Asia also advanced, with South Korea's Kospi surging 4.3% and other benchmarks gaining more than 1%.
The gains followed a US stock market rally on Friday, with the S&P 500 up 2% for its best day since May and the Dow Jones Industrial Average soaring 1,206 points to top 50,000 for the first time.
NHK reported that Takaichi's Liberal Democratic Party alone secured 316 seats in the 465-member lower house, surpassing the previous record of 300 seats won in 1986.
Takaichi's first major task when the lower house reconvenes in mid-February is to work on a budget bill to fund economic measures addressing rising costs and sluggish wages.
