Green MP Chlöe Swarbrick is engaged to her partner, Nadine Walker.
The first-term MP confirmed the happy news to NZME, but offered no further comment.
It's understood the pair were engaged for some months before the news became public, and both are known to be private about their relationship.
"We are very happy for them but we are respecting their privacy during this exciting time," a Green Party spokesperson told Stuff.
Swarbrick has been an MP since 2017, and at 23 years old was the youngest politician to enter Parliament since 1975 when 23-year-old Marylin Waring became an MP for the National Party.
Swarbrick launched to international fame late last year when she responded "OK Boomer" to fellow politician Todd Muller during Parliament's Question Time. The statement made headlines across the world and brought the tension between the generations to the world stage.
She is known for her work for drug reform and harm reduction, as well as climate change policy.
All of the Green Party's MPs voted in favour of legalising gay marriage in 2013.