Foundries are in-universe manufacturers of weapons.
Weapons from a specific foundry will usually have a similar design and function, as well as naming convention. There are also Origin Traits that are associated with specific foundries.
In-game, a weapon's foundry can be identified by a watermark logo in the upper-left corner of the weapon's Details screen. However, not every foundry is represented by one of these logos. The other foundries can only be determined by supplementary material such as Lore, or by logos and iconography seen on the weapon's models. There are also many weapons that do not belong to any known foundry.
The most prominent foundries are Häkke, Omolon, SUROS, and VEIST. Weapons from these foundries can often be found in the World Loot Pool, or as rewards from core playlist activities, including Vanguard activities, the Crucible, Iron Banner, Trials of Osiris, and Gambit.
List of Foundries
The following foundries have logos shown on their weapons' Details screens identifying them:
The following foundry does not have a logo shown on its weapons' Details screens: