Millennials, also known as Generation Y or Gen Y, are the demographic cohort following Generation X and preceding Generation Z. Researchers and popular media use the early 1980s as starting birth years and the mid-1990s to early 2000s as ending birth years, with the generation typically being defined as people born from 1981 to 1996. Most millennials are the children of baby boomers and older Generation X; millennials are often the parents of Generation Alpha.

Across the globe, young people have postponed marriage. Millennials were born at a time of declining fertility rates around the world, and are having fewer children than their predecessors. Those in developing nations will continue to constitute the bulk of global population growth. In the developed world, young people of the 2010s were less inclined to have sexual intercourse compared to their predecessors when they were at the same age. In the West, they are less likely to be religious than their predecessors, but they may identify as spiritual.

Millennials have been described as the first global generation and the first generation that grew up in the Internet age. The generation is generally marked by elevated usage of and familiarity with the Internet, mobile devices, and social media, which is why they are sometimes termed digital natives. Between the 1990s and the 2010s, people from the developing world became increasingly well educated, a factor that boosted economic growth in these countries. Millennials across the world have suffered significant economic disruption since starting their working lives; many faced high levels of youth unemployment during their early years in the labour market in the wake of the Great Recession, and suffered another recession in 2020 due to the COVID-19 pandemic.