A Robeast is a Kaiju-sized monster, more often than not the same size as the Super Robot that battles it, though Robeasts in Sentai and Toku may also start in human size, so as to be a threat on a personal scale, then grows through some form of Applied Phlebotinum.
Robeasts are rarely capable of human-level intelligence or communication, and even when they are, usually prefer to just roar instead.
Robeasts are usually built with both biological and mechanical construction (though some are also completely mechanical, magical constructs, giant demons, and the like). They come in a dizzying variety of shapes, abilities, and weapons, and very rarely will any two robeasts look alike, even between robeasts deployed by the same villain(s). Many of them avoid humanoid designs and mook status, becoming a Mechanical Monster.
- Go Nagai's Mazinger Z is the Trope Codifier; in fact, the monsters in this series are actually called "Machine Beasts (Japanese Kikaiju). The sequel Great Mazinger had Battle Beasts (Sentoujuu) and UFO Robo Grendizer had the Saucer Beasts and Vega Monsters.
- And the Battle Beasts from Great Mazinger already diferred from the Mazinger Z Robeasts, bordering on a Deconstruction from the trope. They were capable of speech and independant thought, and they were Dangerously Genre Savvy thank to it. This resulted in a Eucatastrophe in the THIRD chapter.
- And sometimes Mazinger Z averted or subverted the trope. Some Mechanical Beasts were size-shifters, and some of them -Blazas S1 and S2- were human-sized.
- Voltron is the Trope Namer, after the monsters in GoLion and Dairugger XV.
- Zonders and later Primevals from GaoGaiGar (EI-13 pictured above).
- Zeravire from Gravion.
- The Angels from Neon Genesis Evangelion are an interesting example. At first, they're made out to be gigantic monsters. Then we find out that they are humans as humans could have been had they evolved differently.
- The standard Monster of the Week in Tadao Nagahama's Robot Romance Trilogy
- The Mecha Boosts from Zambot 3
- The Megaborg from Daitarn 3
- The Haniwa Phantom Gods from Kotetsu Jeeg
- The Mimetic Beasts from Shinkon Gattai Godannar
- The Beastmen Ganmen / Gunmen and the Anti-Spiral Mugann from Tengen Toppa Gurren Lagann.
- Gunmen are also an inversion, because the heroes use the exact same kinds of robots they stole from the beastmen.
- Mechasauruses and Mecha Oni from the Getter Robo series
- Slightly inverted in that the Mechasauruses, like much of the Reptilians, are a highly intelligent race.
- S-1 machines of the Aldebaren Army in Space Warrior Baldios.
- Renegade Units in Saber Rider and the Star Sheriffs.
- Cosmosauruses in God Sigma
- Numerous monomakia from Brigadoon Marin and Melan fit this trope.
- Various mechs and creatures from The Big O
- The minions of the Shadow Angels, usually cherubim, in Genesis of Aquarion.
- Kyoshin in Neo Ranga, although somewhat subverted as they stay in two episodes at a time and do not start showing up until episode 17.
- The original form of Mechagodzilla. The second version was a human piloted mecha. The third version was a human piloted mecha built on the bones of the original Godzilla, dubbed Kiryu. Kiryu went berserk in its first confrontaion with (a second) Godzilla, playing with the trope.
Live Action TV
- Every single Ultraman series and movie has these, so much so they even made a spin off featuring the monsters called Ultra Galaxy Monster Battle
- Power Rangers and the rest of the Toku genre revolve around this, with a different rubber suit Monster of the Week to challenge the heroes (and, in Power Rangers and Super Sentai, their machines) as the driving force behind the villain's scheme. Every Big Bad has his or her own way of making monsters, and making them bigger. They're sometimes the source of Nightmare Fuel, and sometimes Narm Charm. Sentience and whether or not they're Exclusively Evil varies from series to series.
- Pretty much everything in Monsterpocalypse. For extra fun, the same company has released completely-compatible Voltron units, so the game has actual Robeasts.
- Any Super Robot Wars game has one or more of the above series included, so it's a given.
- Except for the Original Generation series, which still manages a less "of the week" variant with the Einst. The Shura attempt a more direct homage with their animal-themed mecha, but they have soldiers as pilots. They also get giant space flounder monsters living amidst the asteroid belt.
- Drache, the first boss from Einhander seems to fit. The background story notes that its AI emulates beasts' behaviors. Hence why the robot roars when you defeat it.
- South Park—In the Sentai parody episode, Barbara Streisand turned into a Mechagodzilla.
- And returned in "201" with full sentience.
- Parodied in one episode of The Grim Adventures of Billy and Mandy where Grim takes Billy (who has been transformed into a 50-foot superhero) to Tokyo to meet a spoof of Gidora. An angry Mandy pilotes a giant gorilla robot called Mega-gorillasaur to bring them back.
- The mecha-Stock Ness Monster in the Inspector Gadget episode "Monster Lake".