Three civic and political organizations are organizing the event to encourage the general public and politicians to take a more open approach to sexual minorities.
Dubbed the "the wedding of the century" on social networks, the demonstration will take place two days before Feb. 16, when the modern state of Lithuania celebrates its centennial anniversary.
All couplies will be "married" by Artūras Rudomanskis, one of the organizers of the event dressed as a robot.
Those in favor of regulating by law same-sex relationship say that homosexual couples in Lithuania are now discriminated against, because such people have no right to inheritance or automatic access to information about their partner's health in an emergency, and they cannot represent each other in court proceedings.
Critics of legalization of same-sex marriage and partnership say that homosexual couples are not traditional families and that putting in place regulation of their relationship would be a step toward allowing sexual minorities to adopt children.
Liberal politicians in Lithuania have repeatedly proposed legalization of civil partnership of same-sex couples, however, the initiatives never reached the adoption stage at the parliament.
A survey found in October 2016 that 11 percent of Lithuanians would support same-sex partnership and seven percent would favor the idea of legalizing homosexual marriage.