Production information
Manufacturer Diplan 'Mechyards of Ozawa
Production Year 2660[1][2][3]
Model MON-66
Class Light
Cost 2,229,479 C-bills
Technical specifications
Mech type Inner Sphere BattleMech
Mass 25 tons
Chassis Kell/D Endo Steel
Armor Mitchell GA3 Ferro-Fibrous
Engine Nissan 200
Communications System ON-5
Targeting Tracking System Beagle Active Probe
Heat Sinks 10
Speed 130 km/h
BV (1.0) 633[4]
BV (2.0) 758[5]


The Mongoose BattleMech was introduced in 2660 as a deep recon 'Mech and a direct competitor (and hopeful replacement) for the Locust. As the 'Mech reached Star League Defense Force units though, it was found that the Beagle Active Probe on the Mongoose gave it extremely good command and control features that endeared it to light 'Mech command lances. Within eight years of its introduction the Mongoose was the standard command 'Mech for all light and recon lances. Due to its advanced electronics the Mongoose was capable of coordinating the maneuverings of an entire company of light 'Mechs and at the same time could engage medium 'Mechs with some success thanks to its weaponry and armoring.[1][2][3][6]

Its popularity ensured that the Mongoose had a target on its back after the dissolution of the Star League. The start of the Succession Wars went poorly for the Mongoose when its factory on Ozawa was destroyed in 2837. The loss of the factory meant the 'Mech was already becoming a rarity by the Second Succession War and with many of its components now lostech surviving Mongooses were forced to make-do with inferior spare parts. This was especially true for the Beagle Active Probe, and by the end of the Succession Wars not a single operational Mongoose serving the Great Houses had a functioning example. This trend was reversed with the recovery of the Helm Memory Core and many Mongooses were rebuilt to their former glory. ComStar was also revealed to have kept many Mongooses in their secret storage facilities which they used to outfit the Com Guards. Diplan 'MechYards eventually restarted Mongoose production from their factory on Aix-la-Chapelle and the design would continue to see use for years to come, including during the Jihad.[1][2][3][6][7]

Weapons and Equipment[edit]

The weaponry of the Mongoose consists of three Sorenstein Medium Lasers split between the left arm, right arm and center torso, and one Starflash Plus Small Laser in the head. This light laser array, while not as deadly as most pilots would prefer, is typical of light 'Mechs and makes the Mongoose a highly independent unit that does not need to rely on a supply chain of ammunition for its survival when on recon duties. The centerline lasers in particular are extremely accurate thanks to special internal compensators, allowing precise fire even at a full run. Unfortunately the center torso laser rests right atop the Nissan 200 fusion engine, requiring replacement of the cooling jackets after a hundred firings. While not a difficult item to replace it can become an issue during extended campaigns. The extra heat from both laser and engine can also sometimes interfere with the sensor system and makes the cockpit uncomfortable.[1][2][3]

The Kell/D Chassis around which the Mongoose is built uses Endo Steel construction techniques that, combined with an all energy weapon armament and standard engine, made the Mongoose very sturdy for its size. This also allows it to mount five tons of Ferro-Fibrous armor, much more than other light 'Mechs and gives the Mongoose the capability to survive a direct PPC hit to the chest without suffering internal damage. A top speed of 129 km/h and cruising speed of 86 km/h, one of the fastest of any 'Mech, makes up for the lack of jump jets on the design. Only ten heat sinks means the 'Mech is liable to run hot if the pilot is not careful, especially when the cooling jacket protecting the center torso laser fails.[1][2][3]


  • Mongoose C 2 
    The Mongoose C 2 served as a testbed for Clan Mongoose's newly-developed Targeting Computer technology, dropping a number of double heat sinks to free up the weight required. The success of this variant would ensure the Smoke Jaguars retained the Targeting Computer for their own use, and the technology would later proliferate among all the Clans.[8]
  • MON-66b 
    The 66b is an upgraded version of the 66 that was used by the SLDF Royal units in 2740. It utilizes an XL engine and double heat sinks with the weight savings used to upgrade the center torso medium laser to an ER Large Laser.[9] BV (2.0)= 934[10][11]
  • MON-67 
    The MON-67 is the downgraded version of the MON-66 Mongoose introduced in 2830. The MON-67 removes the active probe and replaces the Endo Steel structure with a standard structure while the armor has been downgraded to standard plate armor. To keep the same level of protection as before, half a ton of armor has been added to the Mongoose. BV (1.0) = 612[12], BV (2.0) = 741[13] [14]
  • MON-68 
    This variant of the downgraded MON-67 introduced in 3039 by the DCMS removes all the standard weaponry in exchange for a single Large Laser. The swap to a lighter 175 rated engine reduced the MON-68's ground speed by 10 km/h. BV (2.0) = 676 [15]
  • MON-69 
    A variant of the MON-66 introduced in 2819, the MON-69 replaced the LosTech active probe with an SRM-2 and one ton of reloads since the advanced electronics were difficult to come by during the Succession Wars. In order to make this possible, a half ton of armor was also removed. BV (2.0) = 737 [16]
  • MON-70 
    The MON-70 dates to 2819 and was another variant of the standard MON-66 introduced following the loss of the active probe. In addition to removing the Beagle, it also replaces the small laser with a pair of Flamers. BV = 750[17]
  • MON-76 
    The MON-76 is an upgrade of the Mongoose introduced in 3077. The original electronics, weapons, engine, and cooling system have been stripped from the chassis and the design was completely rebuilt. As far as the engine, the original Nissan 200 was replaced with an ExtraLight version and includes a MASC system allowing for incredible bursts of speed. Next, the standard heat sinks originally found on the 'Mech were replaced with double strength units. The original Beagle Active Probe was replaced with a Guardian ECM Suite to allow the Mongoose to interfere with enemy electronics, and the original medium lasers have been replaced with Medium Pulse Lasers. BV (1.0) = 724[18][19], BV (2.0) = 894[20]
  • MON-86 
    Upgraded to use a Light PPC and XL engine, the MON-86 introduced in 3078 has a top speed close to 150 km/h. It also has a medium laser in each arm, while the right torso has an ER Small Laser. The MON-86 keeps the head-mounted small laser of the original Mongoose and the Beagle Probe for scout duty.[21] BV (2.0) = 887[22]
  • MON-96 
    An XL engine propels this model at a top speed of 120 km/h, but the engine Supercharger lets it sprint to 160 km/h briefly. It has an ER Medium Laser in each arm and the center torso supplemented with an ER Small Laser in the head. The high ground speed of the Mongoose allows it to carry the Bloodhound Active Probe into and out of combat quickly. Protection is provided by Heavy Ferro-Fibrous armor. BV (2.0) = 1,011[23]

Custom Variants[edit]

  • MON-66GX Mongoose Gunslinger 
    This Mongoose variant was developed for the SLDF Gunslinger Program, but never saw service. It kept the Mongoose ground speed, but stripped out the electronic equipment for more weaponry. Two medium lasers were in each arm, while a single torso mounted SRM-6 with a ton of ammunition was mounted in the chest. To offset the loss of the advanced electronics, this chassis was equipped with a Null Signature System and a Chameleon Light Polarization Shield. It also carried six tons of armor.[24] BV (2.0) = 974[25]

Related BattleMechs[edit]

  • Beowulf - After the Word of Blake captured Terra in 3058, Comstar decided to replace their lost Mongoose BattleMechs with new Beowulf 45-ton BattleMechs. It is equipped with an XL engine and mounts far more armor, better weapons, and is jump capable[26].

Design Quirks[edit]

The Mongoose has the following Design Quirks:[28]

The MON-66GX Mongoose Gunslinger variant is subject to the following Design Quirks:[24]


In German products the unit's proper name was perfectly translated to Mungo. The model code was accordingly changed to MUN-66.



  1. 1.0 1.1 1.2 1.3 1.4 Technical Readout: 2750, pp. 20-21
  2. 2.0 2.1 2.2 2.3 2.4 Technical Readout: 3050 Upgrade, pp. 188-189
  3. 3.0 3.1 3.2 3.3 3.4 Technical Readout: 3039, pp. 246-247
  4. Combat Operations, p. 107
  5. Record Sheets: 3050 Upgrade (Clan & Star League), p. ??
  6. 6.0 6.1 Technical Readout: 3025 Revised, p. 12-13
  7. Objectives: Draconis Combine, p. 17
  8. 8.0 8.1 Technical Readout: Golden Century, pp. 10-11 "Mongoose C"
  9. Technical Readout: 3075, p. 169
  10. Record Sheets: 3075 Unabridged, p. 155
  11. Record Sheets: 3075 Unabridged - Age of War, p. 15
  12. Combat Operations, p. 125
  13. Record Sheets: 3039, p. 68
  14. Record Sheets: 3039 Unabridged, p. 404 "Mongoose MON-67"
  15. Record Sheets: 3039 Unabridged, p. 405 "Mongoose MON-68"
  16. Record Sheets: 3050 Unabridged - Clans & Star League, p. 228 "Mongoose MON-69"
  17. Record Sheets: 3050 Upgrade (Inner Sphere), p. 59
  18. Combat Operations, p. 134
  19. Record Sheets: Upgrades, p. 39
  20. Record Sheets: 3050 Upgrade (Inner Sphere), p. 60
  21. Technical Readout: 3085, p. 190
  22. Record Sheets: 3085 Unabridged — Old is the New New, p. 59
  23. Recognition Guide: ilClan, vol. 10, p. 17
  24. 24.0 24.1 Experimental Technical Readout: Gunslingers, p. 3
  25. Experimental Technical Readout: Gunslingers, p. 16
  26. Technical Readout: 3060, p. 88
  27. Technical Readout: 3075, p. 72
  28. BattleMech Manual, p. 93 BattleMech Quirk Table - Mongoose Entry.