Hip-hop or hip hop (formerly known as disco rap) is a genre of popular music that emerged in the early 1970s in New York City. The genre is characterized by stylized rhythmic sounds—often built around disco grooves, electronic drum beats, and rapping, a percussive vocal delivery of rhymed poetic speech as consciousness-raising expression. The music developed as part of the broader hip-hop culture; while often used to refer solely to rapping and rap music, "hip-hop" more properly denotes the practice(s) of the entire subculture. The term hip-hop music is sometimes used synonymously with the term rap music, though rapping may not be the focus of hip-hop music. The genre also centers DJing, turntablism, scratching, beatboxing, and instrumental tracks.

Hip-hop as both a musical genre and a culture was formed during the 1970s, when block parties became increasingly popular in New York City, particularly among ethnic minority youth residing in the Bronx. At block parties, DJs played percussive breaks of popular songs using two turntables and a DJ mixer to be able to play breaks from two copies of the same record, alternating from one to the other and extending the "break". Hip-hop's early evolution occurred as sampling technology and drum machines became widely available and affordable. Turntablist techniques such as scratching and beatmatching developed along with the breaks. Rapping developed as a vocal style in which the artist speaks or chants along rhythmically with an instrumental or synthesized beat.

Hip-hop music was not officially recorded to play on radio or television until 1979, largely due to poverty during the genre's birth and lack of acceptance outside ghetto neighborhoods. The genre of music began spreading through block parties throughout the Black community. Old-school hip hop was the first mainstream wave of the genre, marked by its disco influence and party-oriented lyrics. The 1980s marked the diversification of hip-hop as the genre developed more complex styles and spread around the world. New-school hip hop was the genre's second wave, marked by its electro sound, and led into golden age hip hop, an innovative period between the mid-1980s and mid-1990s that also developed hip-hop's own album era. The gangsta rap subgenre, focused on the violent lifestyles and impoverished conditions of inner-city African American youth, gained popularity at this time. West Coast hip hop was dominated by G-funk in the early-mid 1990s, while East Coast hip hop was dominated by jazz rap, alternative hip hop, and hardcore hip hop. Hip-hop continued to diversify at this time with other regional styles emerging, such as Southern rap and Atlanta hip hop. Hip-hop became a best-selling genre in the mid-1990s and the top-selling music genre by 1999. Hip-hop became a category at the Grammy Awards in 1989 with the addition of the Best Rap Performance award and was given to DJ Jazzy Jeff & the Fresh Prince for their song "Parents Just Don't Understand". In 1990, they became the first hip-hop act to perform at the Grammys.

The popularity of hip-hop music continued through the late 1990s to early-2000s "bling era" with hip-hop influences increasingly finding their way into other genres of popular music, such as neo soul, nu metal, and R&B. The United States also saw the success of regional styles such as crunk, a Southern genre that emphasized the beats and music more than the lyrics, and alternative hip-hop began to secure a place in the mainstream, due in part to the crossover success of its artists. During the late 2000s and early 2010s "blog era", rappers were able to build up a following through online methods of music distribution, such as social media and blogs, and mainstream hip-hop took on a more melodic, sensitive direction following the commercial decline of gangsta rap. The trap and mumble rap subgenres have become the most popular form of hip-hop during the mid-late 2010s and early 2020s. In 2017, rock music was usurped by hip-hop as the most popular genre in the United States. In recent years, hip-hop's influence has transcended musical boundaries, impacting fashion, language, and cultural trends worldwide.

Amidst its evolution, hip-hop has also been a vehicle for social commentary and political expression, reflecting the struggles and aspirations of marginalized communities. From its roots in the Bronx to its global reach today, hip-hop has served as a voice for the disenfranchised, shedding light on issues such as racial inequality, poverty, and police brutality. Artists such as Public Enemy, Tupac Shakur, and Kendrick Lamar have used their platforms to address systemic injustices, fostering dialogue and inspiring activism. Hip-hop's ability to confront societal issues while simultaneously providing a form of empowerment and self-expression has solidified its significance beyond mere entertainment, making it a significant cultural force worldwide.