Dressed in matching suits, Shane Lin and Marc Yuan were the first to arrive on Friday at a government office in the capital, Taipei, to sign their marriage certificates.
They were followed by playwright LiYing Chien and her girlfriend, a cartoonist who goes by the pen name Cynical Chick.
Taiwan made history last week when it became the first place in Asia to legalise gay marriage. But the issue has also caused deep divisions on an island that remains staunchly conservative, especially outside of the cities and among older generations.
Some 300 same-sex couples – half of them in Taipei – are expected to register on Friday, according to officials.
The capital’s city hall will co-host an outdoor wedding party near the famous Taipei 101 skyscraper, with local and foreign dignitaries expected to attend.
For veteran gay rights activist Chi Chia-wei, Friday’s weddings are the culmination of a three-decade long fight trying to persuade successive governments to change the law.
It was Chi who eventually petitioned Taiwan’s Constitutional Court leading to a 2017 judgement that denying same-sex couples the right to marry was unconstitutional.
Facing an imminent court deadline, parliament finally passed a bill on May 17 allowing same-sex couples to form “exclusive permanent unions” and another clause that would let them apply for a “marriage registration” with government agencies.
“I feel very happy that same-sex couples can finally register and be listed as each other’s spouse. I am honoured to witness Friday’s marriage registrations,” Chi told told AFP news agency.
In the last decade, Taiwan has placed itself at the vanguard of gay rights in Asia but the issue has polarised society.
Conservative and religious groups mobilised after the court ruling and comfortably won a series of referendums last November in which voters comprehensively rejected defining marriage as anything other than a union between a man and a woman.
Conservative lawmakers put forward rival bills that offered something closer to limited same-sex unions but those measures failed as parliament comfortably passed the gay marriage law.
However, the new law still has restrictions not faced by heterosexual couples.
Same-sex couples can currently only adopt their partners’ biological children and can only wed foreigners from countries where gay marriage is also recognised.
Gay rights groups say they are willing to accept partial equality for now in the hopes of winning later legal battles over issues such as adoption, surrogacy and marrying foreigners.
Opponents have vowed to punish President Tsai Ing-wen and the politicians who supported the gay marriage law in the January 2020 elections when the Taiwanese will elect both a new president and a new parliament.