Aldi (stylized as ALDI) is the common brand of two German family-owned discount supermarket chains with over 10,000 stores in 20 countries, and an estimated combined turnover of more than €50 billion.

The chain was founded by brothers Karl and Theo Albrecht in 1946 when they took over their mother's store in Essen. The business was split into two separate groups in 1960, that later became Aldi Nord, headquartered in Essen, and Aldi Süd, headquartered in Mülheim. In 1962, they introduced the name Aldi (a syllabic abbreviation for Albrecht Diskont).

Aldi's German operations consist of Aldi Nord's 35 individual regional companies with about 2,500 stores in western, northern, and eastern Germany, and Aldi Süd's 32 regional companies with 1,600 stores in western and southern Germany.

Internationally, Aldi Nord operates in Denmark, France, the Benelux countries, Portugal, Spain and Poland, while Aldi Süd operates in Ireland, the United Kingdom, Hungary, Switzerland, Australia, China, Italy, Austria and Slovenia.

Both Aldi Nord (as Trader Joe's) and Aldi Süd (as Aldi) also operate in the United States with 1,600 stores between them as of 2017 (and the U.S. is the only country to have both Aldi companies operating outside of Germany).

According to Statista, Aldi is the most valuable German food retail brand in 2020, ranked at 14.6 billion U.S. dollars.

According to Statista and en.wikipedia