A data repository is an IT system that stores data sets.
This post is an introduction to data repositories.
List of open data repositories
OpenML.org
OpenML.org
Kaggle Datasets
Kaggle Dataset official website
Papers with Code
Paperswithcode.com
UC Irvine Machine Learning Repository
https://archive.ics.uci.edu
https://archive.ics.uci.edu/datasets
AWS Open Data
Registry.opendata.aws
TensorFlow Datasets
Tensorflow.org/datasets
IEEE Open Datasets
European Union Open Datasets
Portal de datos en abierto de la Unión Europea
UNED
Government of Spain
Datos en abierto del Gobierno de España
Bank of Spain’s Statistics
Bank of Spain Data Portal
Bank of Spain Statistics + Bank of Spain Data Laboratory
Bank of Spain Data Portal official website
Madrid Town Hall Open Data
Datos en abierto del ayuntamiento de Madrid
Metaportals with data
Dataportals.org
Dataportals.org
Opendatamonitor.eu
Opendatamonitor.eu
Wikipedia
List of datasets for machine-learning research
Where can I find large datasets open to the public? at Quora
Where can I find large datasets open to the public? at Quora