Largely intended to be BattleMechs piloted by notable characters from the BattleTech universe, "Hero 'Mechs" are a sub-group of special 'Mechs introduced by Piranha Games, Inc. in the MechWarrior Online and MechWarrior 5: Mercenaries computer games.
Originally introduced by PGI for MechWarrior Online, within the MWO game Hero 'Mechs are exclusive variants which can only be purchased with real money in what is otherwise essentially a free-to-play online game. They offer a unique paint scheme, a per-match C-Bill booster (currently 30%), and a custom hardpoint layout.
The Hero 'Mechs were originally based on certain individual named 'Mechs from established BattleTech lore or the otherwise unnamed individual 'Mechs of certain famous MechWarriors, especially the "Notable 'Mechs and MechWarrior" sections from Technical Readouts (and here, from the seminal Technical Readout: 3025 in particular). It should be noted, however, that the customized configurations of these 'Mechs and in some cases also their names were created for MWO; in the original source(s) there was usually no indication that the 'Mech in question was anything other but a regular model. Others were invented for MWO whole cloth, with no previous mention of either the 'Mech or its pilot in canon.
A selection of Hero 'Mechs introduced in MWO were also among the available variants in PGI's MechWarrior 5: Mercenaries. Reflecting their unique status, Hero 'Mechs are an uncommon sight in the game's industrial hubs with a special icon to alert the player when they do appear for sale.
Notably, the descriptive fluff texts for the Hero 'Mechs have been declared fully canonical for the BattleTech universe by then-incumbent Catalyst Game Labs Line Developer, Randall N. Bills, who also provided most if not all of these texts. That means by extension that the 'Mechs as such are canon even when not otherwise mentioned in BattleTech lore, but only to the extent described in the accompanying fluff text. By contrast, their in-game stats and appearance are apocryphal unless mentioned in the fluff text, and in case of clashes with established BattleTech lore such as anachronistic equipment are overruled by the established canon. With the release of BattleTech: Legends a number of unique names first introduced in MWO were used, though with configurations and equipment that do not match their MWO counterparts.
MWO has since published several original 'Mech designs, and Hero 'Mechs were created and fluffed for these as well. Assistant Line Developer Ray "Adrian Gideon" Arrastia expressly clarified the original designs from PGI are not canonical, regardless of any Hero 'Mechs or Hero 'Mech fluff associated with them.
- In this posting on the official BattleTech Forum by Ray "Adrian Gideon" Arrastia, regarding the canon status of PGI-exclusive 'Mechs for which record sheets had been brought to Mech_Con 2018: "Those sheets are not official and those designs are not canon for the tabletop. CGL cannot use the PGI-created designs, no matter what “part” CGL or its employees play in the creation of the designs. When asked for confirmation, Randall and Brent stated that those were provided by a demo agent and they allowed it *this time only* as part of the hype at Mech_Con."