VLVnT 2021 is the 9th edition of the Very Large Volume Neutrino Telescope Workshop and will take place in the online format between 18 and 21 May 2021, in Valencia, Spain. The previous editions were held in Amsterdam (2003), Catania (2005), Toulon(2008), Athens (2009), Erlangen (2011), Stockholm (2013), Rome (2016) and Dubna (2018). The conference is focused on progress of neutrino and multi-messenger astronomy, in particular the physics, technological and instrumental aspects of large-scale detectors in water or ice. It is foreseen the participation of industrial partners that will make possible to discuss future applications in the neutrino and multi-messenger astronomy.