The Crystal Palace loanee was given his debut by Dougie Freedman at Selhurst Park.
The Welsh international arrives on loan until January where he will be hoping to get his recently injury plagued career back on track.
In joining Forest he will also be teaming up with Dougie Freedman once again. When he made his Palace debut in August 2011, at the tender age of 17, it was Freedman who subbed him onto the field against Coventry City.
Freedman gave him his break in football and now Williams has confirmed that playing under the Scot at the City Ground was a major factor in his decision to head to the club on loan.
Speaking to BBC Nottingham Sport the 21-year-old stated:
"I can't thank him enough because he gave me my breakthrough in the football world.
"That was a good factor in coming here."
Williams has not played a game since April and featured only 12 times last season for both Palace and former loan team Ipswich Town. Therefore he will need to work hard on his fitness first before he becomes a regular in the Forest line-up.
But whilst many have forgotten, Freedman will be well aware of what a fully-fit Williams can do at this level and hopefully that is exactly what Forest will see from the player.