Banco Santander, S.A., doing business as Santander Group (UK: /ˌsæntənˈdɛər, -tæn-/, US: /ˌsɑːntɑːnˈdɛər/,[2][3] Spanish: [santanˈdeɾ]), is a Spanish multinational financial services company based in Madrid and Santander in Spain. Additionally, Santander maintains a presence in all global financial centres as the 16th-largest banking institution in the world. Although known for its European banking operations, it has extended operations across North and South America, and more recently in continental Asia. It is considered a systemically important bank by Financial Stability Board.

Many subsidiaries, such as Abbey National, have been rebranded under the Santander name. The company is a component of the Euro Stoxx 50 stock market index. In May 2016, Santander was ranked as 37th in the Forbes Global 2000 list of the world's biggest public companies. Santander is Spain's largest bank.[4]

As of 2017, Santander is the 4th largest bank in Europe with approximately US$1.4 trillion in total assets-under-management (AUM).[5] Traded on the Euro Stoxx 50 stock market index, the bank has a total market capitalization of $69.9 billion.[6] As of 2019 it has €3.9 trillion in assets under custody (AUC) and €2.1 trillion in assets under administracion (AUA).[7] It is chaired by Ana Patricia Botín-Sanz de Sautuola O'Shea, daughter and granddaughter of erstwhile chairmen, Emilio Botin-Sanz de Sautuola y García de los Ríos and Emilio Botín-Sanz de Sautuola López, respectively.