Since the late 1940s, the government of South Korea had implemented a ban of all Japanese media, since Japan attacked South Korea during World War II. For this reason, famous Japanese kaiju films such as Godzilla had never appeared in the South Korean market at the time.
In 1967, however, a kaiju film directed by little-known filmmaker Kim Ki-duk known as Yonggary had appeared in South Korean cinemas, gaining Ki-duk and this movie a cult status outside of South Korea in the process. The film could also be referred to by some as the "Korean Godzilla", and is also similar to Robot Taekwon V, a cult classic that was the Korean counterpart to the Japanese Super Robot anime Mazinger Z.
The two main actors in this movie are Oh Yeong-il and Nam Jeong-im, and they might've also got a cult status because of this movie.
The film begins with a massive bomb that is explodes in the Middle East, generating earthquakes as the result of its impact. A young South Korean couple is planning to get married until Yonggary, a giant monster from Korean folklore, emerges from out of the sea, causing another massive earthquake that comes to the Korean peninsula. Apparently, the only fluid that Yonggary can survive on is oil, so he attacks Seoul's oil refineries. However, the oil refineries were shut off in order to prevent Yonggary from attacking the city once more. The monster eventually gets killed, and I believe that the couple gets married at the end (I haven't seen the movie or parts of it in general).
In the United States, Yonggary gained an immense cult following amongst fans of both monster movies and kaiju films, or otherwise certain nerds in general. It is widely available on DVD in the United States, too, but the only format of this movie that is currently available is the AIP-TV English dub (the original Korean negative was lost, unfortunately), like how many of the Godzilla movies were dubbed into English, too.
South Korean comedian and filmmaker Shim Hyung-rae (possibly) wanted to cash-in on the 1998 Godzilla movie by producing, directing and releasing a remake of Yonggary in 1999. The movie was released in the United States, given the title Reptilian. The film did get negative reviews upon release, but, just like the original Yonggary from 1967, it did become a cult classic.