The winger joined on a five-year deal from Bournemouth last week.
The Magpies paid Bournemouth £10 million for the Scotland international, who signed a five-year deal at St. James' Park last week.
The pull of joining a club such as Newcastle, even after their relegation, is understandable, and Ritchie revealed that it was also the thought of working with such a prestigious manager as Benitez which convinced him to make the move.
The 26-year-old told reporters, as quoted by the Shields Gazette: "I loved my time at Bournemouth, it was very successful. But when a club like Newcastle comes calling, with the position it has and the manager, it was always going to be a difficult one to turn down.
"He [Benitez] is a massive draw. He's won just about everything there is to win in football and I'm really looking forward to working with him."
Newcastle fans will now be hoping that Ritchie can replicate the form he showed for Bournemouth for the Magpies this season as the Tyneside club chase immediate promotion back to the Premier League.
Though he managed just four strikes in the top flight last term, in the Cherries' promotion-winning season of 2014-15 the winger netted 15 times in 46 appearances.