Forcas III is the third planet in the Forcas system in the Klingon Empire.
Worf entered a bat'leth competition here in 2370, and won Champion Standing. (TNG: "Parallels")
In that episode, Worf experienced multiple quantum realities, in some of which his results at the competition, and even his attendance, were different.
Forcas III was the origin of a drink that Guinan served in Ten Forward on the USS Enterprise-D. When Data tried this drink, during one of his first experiences with his emotion chip, he described the Forcas III drink as "revolting". (Star Trek Generations)