The Noun Project - Creating, Sharing and Celebrating the World's Visual Language
macOS Big Sur icons - Original icons in PNG ready for download
Nucleo - Commercial vector icons and accompanying apps to manage and customize them.
Iconoir - A diverse and open-source library with 900+ icons
Font Awesome - Font Awesome makes it easy to add vector icons and social logos to your website. And version 5 is redesigned and built from the ground up!
IconStore - Free icon packs by first-class designers