The country's most passionately-supported team beat the Orix Buffaloes in the final game of the best-of-seven series late on Sunday night to win the title for the first time since 1985.
It lifted the so-called "Curse of the Colonel", which warned that the Tigers would never win another Japan Series after fans threw a plastic statue of Colonel Sanders snatched from a nearby KFC restaurant into the river the last time they won the title.
Tigers fan Yuko Kawase, who attends about 80 or 90 games a season as well as the team's training camps, told AFP that it felt "like a dream".
"It's been 38 years since the last time, and Hanshin fans who I have known have passed away since then," she said.
"A lot happens in a person's life over the course of 38 years and I have been reflecting on a lot of things."
Police had warned fans not to jump into the Dotonbori River, which authorities had described as like "swimming in toilet water".
One person died after diving in when the Tigers won the Central League pennant in 2003.
But the warning went unheeded after the Tigers' latest victory, with cheers erupting every time a fan hurled themself into the murky water, though no injuries were reported.
One man even arrived for the celebrations dressed as Colonel Sanders, and was duly tossed into the river.
"I'm so happy," said fan Hiroshi Okamoto.
"I want to celebrate the long-awaited moment of victory with everyone."
The Tigers are massively popular in baseball-crazy Osaka, but they have a long history of underachievement.
They last reached the Japan Series in 2014, where they lost the best-of-seven contest 4-1 against the Fukuoka Softbank Hawks.
Their woeful record stands in stark contrast to their Tokyo-based arch-rivals the Yomiuri Giants, who have won the Japan Series 22 times and are considered their country's equivalent of the New York Yankees.
But the Tigers bucked the trend this year, beating the defending champion Buffaloes in seven games to claim the title.
"Each one of them has a role to play, and they all do it well," said Tigers fan Yoko Sakai.
"They play a very connected style of baseball."
