Lyari (Urdu: لیاری; Sindhi: لیاري; Balochi: لێاری) is a historic locality in Karachi, Pakistan. It is the most densely populated part of Karachi, and is one of its earliest settled areas.

Lyari's name is said to be derived from a Sindhi word lyar, a tree which grows along the banks of the river.

Lyari is said to be one of the oldest inhabited parts of Karachi, and is referred to by its residents as the "Mother of Karachi." The first residents of Lyari were Sindhi fishermen and Baloch nomads (pawans). The first influx occurred in 1725, when Sindhi banyas (wāniya) came and expanded it, before Karachi was formally established in 1729. Further waves of Baloch migrants arrived in 1770 and 1795.

The British East India Company captured Karachi on 3 February 1839. After Karachi was developed under British rule, large waves of Baloch migrants settled in the Lyari from Iranian Balochistan.

Lyari's population was 24,600 in 1886, and it was a majority-Muslim area of Karachi, which in turn was majority Hindu. At the time, the Lyari River flowed along the northern edge of Mithadar, with Lyari settlement across the river. As a result, the area was referred to as the Trans-Lyari Quarter during the British period. Lyari was neglected during this era, as the British administrators and Hindu mercantile community showed little interest in developing the Muslim-majority working-class locale, and instead chose to develop the port and eastern part of Karachi. As a result, Lyari developed in a haphazard manner, and was characterized by a cluster of poor settlements with home made of reed and mudbrick. One quarter of Karachi's entire population lived in the Trans-Lyari Quarter at the turn of the 20th century.

Migration of Iranian Baloch increased after some political unrest in parts of Iranian Balochistan in 1928. In 1941, the population of Lyari was 81,768.

After independence, neglect of Lyari continued. Development of Lyari at this time was focused on the northern outskirts, and included the planned neighborhoods of Agra Taj Colony and Bihar Colony - both of which were developed for migrants. By 1956, Lyari's population had rapidly grown to about 360,000. In the late 1950s, General Ayub Khan attempted to rehabilitate central Karachi by relocating Lyari's population to the northern neighborhood of New Karachi, which was fiercely opposed by the residents despite Lyari having no basic amenities at the time.

Lyari's first criminal gangs took root in the 1960s, but were considered to be fairly harmless towards the local population. In the late 1970s, Lyari gave rise to its own music scene, known as "Lyari Disco." Lyari in the 70s also became a haven for drug traffickers who could avoid law enforcement agencies in the localities narrow lanes. By the 1980s, weapons from the Soviet–Afghan War arrived in Lyari, and drug-addiction became widespread. Some locals allege that drugs were pushed into the neighbourhood by the regime of Zia-ul-Haq in retaliation for Lyari's opposition to his rule. In 1987, Benazir Bhutto was elected to the National Assembly from a seat in Lyari.