Armley is a district in the west of Leeds, West Yorkshire, England. It starts less than 1 mile (1.6 km) from Leeds city centre. Like much of Leeds, Armley grew in the Industrial Revolution and had several mills, one of which now houses the Leeds Industrial Museum at Armley Mills. Armley was historically – and predominantly still is – a largely working-class area of the city; it retains many smaller industrial businesses, and has many rows of back-to-back terraced houses.

It sits in the Armley ward of Leeds City Council and Leeds West and Pudsey parliamentary constituency.

In 2022, statistics released by West Yorkshire Police revealed Armley and New Wortley had the second highest crime rate in Leeds after Leeds city centre.

First attested in Domesday Book of 1086 as Ermelai, the name Armley comes from Old English. The second element is from Old English lēah ('open space in a wood'). The origin of the first element is less clear, but thought to come from an otherwise unattested Old English name Earma, a plausible nickname form of the name Earnmund. If so, the name originally meant 'Earma's woodland clearing'.

Historically lying within the township of Armley, to the south of Armley's centre, the district of Green Side is first mentioned by this name in the nineteenth century. The origin of the name is not certain, but is probably named after the green space now constituted as Wortley Recreation Ground and Western Flatts Cliff park.

Armley is mentioned in the 1086 Domesday Book reference to "Ristone, Ermelai". At the time there were eight villagers in Ristone (now east Armley) and Ermelai (now west Armley). Armley was recorded as lying within the hundred of Morley and was estimated to comprise only four households, placing it in the bottom fifth of settlements in the Domesday Book by population size. The actual population is indeterminable as this only accounts for the 'head of household'.

Armley Mills, now the Leeds Industrial Museum, was the world's largest woollen mill when it was built in 1788. In the 18th and 19th centuries Armley was, through its mills, a major contributor to the economy of the city of Leeds. Many of the buildings standing in and around Armley were built in the 1800s, including many of the churches, schools, shops and houses. Ledgard Way is named after the entrepreneur Samuel Ledgard. Armley also has picturesque views over the rest of Leeds from certain vantage points. William Tetley started his business of malters in Armley in the 1740s. His grandson Joshua Tetley founded Tetley's Brewery in Hunslet in 1822.

Armley was formerly a township and chapelry in the parish of Leeds. In 1866 Armley became a separate civil parish, but on 26 March 1904 the parish was abolished to form Armley and Bramley. In 1901 the parish had a population of 27,521.