The 29th European Symposium on Artificial Neural Networks, Computational Intelligence and Machine Learning will be organized online, from Wednesday 6 to Friday 8 October 2021. Sanitary forecasts were not sufficiently good when a decision to organize the conference physically or online had to be taken. This remains particularly true regarding the number of people authorized to gather indoor in a single room, and the possibilities of crossing borders. Health and safety of participants remain our top priorities.  ESANN 2021 will be organized online, with interactive sessions for both talks and posters.