Slowcore, also known as sadcore, is a subgenre of indie rock characterised by subdued tempos with typically minimalist instrumentation alongside solemn and melancholic lyrical performances.

The history of slowcore began in the late-1980s with bands forming in reaction to the abrasive sounds of grunge. Slow rock music, akin to singer-songwriter and folk, laid the groundwork for the genre in the early years and until the mid 1990s, where Low played a pivotal role in establishing slowcore as one of the era's microgenres; however, despite their retrospective acclamation as slowcore pioneers, Low was not the first band to produce slowcore. Codeine, Red House Painters, and Bedhead all released influential albums earlier that decade, while American Music Club—widely considered to be the genre's first act—formed in 1982. Regardless, the mellow and restrained sound of Low's debut, I Could Live in Hope (1994), and their albums that followed over the next several years, came to define slowcore. Spain, Duster, and Ida, among others, all followed Low and furthered the reach of the genre, and by the 2000s, slowcore had an obvious sound, even without clear categorisation. Artists like Carissa's Wierd, Jason Molina, and Duster incorporated its archetypical sound in their music throughout the introductory years of the 21st century, while others, including Hope Sandoval & the Warm Inventions, Grouper, and Sun Kil Moon, were more experimental but remained within the genre's confines. Because of slowcore's broad interpretation, observers have described several other musicians and bands as slowcore.

The term "slowcore" derives from "slow", referring to the tempo and energy of the music, and "-core", which refers to a scene, style, or musical subgenre. "Sadcore" imitates similar etymology, and the names are used interchangeably. The term itself has an unclear origin, though sources suggest "slowcore"'s use started in the early 1990s. Scholars and bands alike have shown ambivalence towards the name, with some deeming it pejorative.