Monstroid is a 1980 American monster movie produced and directed by Kenneth Herts (as Kenneth Hartford), co-written with Herbert L. Strock, and starring James Mitchum and John Carradine. Strock later claimed he co-directed the film uncredited. It was originally to be titled Monster when the film was first announced in 1975, and again in 1977, and suffered numerous cast changes (Keenan Wynn was still billed on some of the early video releases). The film was eventually released in 1980 as Monstroid, and is also known as Monstroid: It Came from the Lake (American DVD box title) and The Toxic Horror (American alternative title). A novelization written by Peter Crowcroft was released concurrently with the film. Hartford had his own children (Glen and Andrea) play the two teenagers in the film.

The film billed itself as being based on a true story that took place in "Chimayo, Colombia", in 1971. However, the film was actually shot in Chimayo, New Mexico, and Ambalema, Colombia. Some of the film was also shot in the Santuario de Chimayo, with John Carradine playing a priest.