All official ArcGIS Enterprise software, including ArcGIS Server, is hosted on the My Esri portal.
ArcGIS Server is the backbone of your ArcGIS Enterprise deployment, providing the heavy lifting for web services and geoprocessing. Whether you are setting up a fresh site or upgrading to the latest version, getting the right files is your first step toward building a robust GIS infrastructure.
: Find the "ArcGIS Server" setup file under the core components section and start your download. 2. Generating Your License File
Getting Started: How to Download and License ArcGIS Server Enterprise