OSR stands for "Old School Renaissance." It is an umbrella term encompassing pre-D&D 3.0 versions of Dungeons & Dragons. The various older editions are closely related enough that an answer for one is often applicable to other editions.
This encompasses the following:
- Original Dungeons & Dragons [odnd]
- Basic Dungeons & Dragons (Holmes) [dnd-holmes]
- B/X Dungeons & Dragons (Moldvay/Cook) [dnd-bx]
- BECMI Dungeons & Dragons (Mentzer) [dnd-becmi]
- Advanced Dungeons & Dragons 1st Edition (Gygax) [adnd]
- Advanced Dungeons & Dragons 2nd Edition (Cook) [adnd-2e]
Many reissues of the first rules (pre ADnD) also exist and are classified as OSR too. This includes (alphabetical list, non comprehensive):
- Labyrinth Lord
- OSRIC
- Swords and Wizardry
