Free music and sound effects for your video or game

YouTube Audio Library

Free background music for your videos.
https://www.youtube.com/c/AudioLibraryEN

SoundBible

Free sound clips.
https://soundbible.com/

GDC Game Audio Bundles

Each year they publish 27.5GB+ of high-quality royalty-free sound effects.
Last year bundle: https://gdc.sonniss.com/
Previous years bundles: https://sonniss.com/gameaudiogdc

Pixabay Music and Sound Effects

Royalty-free
https://pixabay.com/music/
https://pixabay.com/sound-effects/

Punchdeck

Free orchestral and electronic music under Creative Commons license.
[Reddit post] [Archive] [YouTube channel]

Bensound

Royalty Free Music for Videos
https://www.bensound.com/

PDSounds.org

Not sure about the license and quality.
https://pdsounds.org/

Splice

Millions of royalty-free one-shots, loops, FX, MIDI and presets. Offers paid plans and requires registration.
https://splice.com/

Free Music Archive

Royalty free music.
https://freemusicarchive.org/

Archive.org

Audio archive
Live music archive

Bonus

56 Best Websites to Create Awesome Royalty Free Sound Effects (archived article from 2014.)