New Zealand's Parliament legislated for marriage equality in 2013, over four and a half years ahead of the passage of similar legislation in Australia. Civil unions came into being in New Zealand in 2005 but had only been enacted at a state and territory level in Australia, often with a different name. How might we account for these divergences? This article offers a comparative account of the Australian and New Zealand situation in order to explain the different trajectories. It marks out some important political, legal, and constitutional contextual issues, personalities, and practices that shaped the ways in which the movement for marriage equality was enabled, resisted, and had an impact on people who wanted to marry.Same-sex couples in New Zealand earned the right to marry in 2013, after a surprisingly low-key public debate, but the Australian situation was very different. Attempts to change Australian federal law still struggled along in 2013, and reform did not come until 2017 following a divisive debate and postal survey. Why did the New Zealand and Australian experience diverge? The nations have some obvious similarities. They are geographically close, separated by the Tasman Sea. Both are settler states, founded on a process of colonisation that transplanted millions of people from the British Isles along with many of their laws, political institutions, social structures, and values. Neither country has an activist judiciary and the Parliaments of both are sovereign in law-making. Trans-Tasman political groupings resemble one another too: the Labour parties have their roots in the union movement, while the centre-right National/Liberal parties have a long tradition of representing rural and business constituencies. At the same time, there are significant differences. Catholicism has long had a powerful influence on the Australian Labor Party, a political organisation that has the most structured factions of any western social democratic political party. 1 Each state and territory has its own factional arrangements arising from its particular union and industrial histories. In several, including the most populous state of New South Wales, the Right faction and unions have prevailed, wielding control over many Labor pre-selection contests. More broadly, New Zealand has