He is the first Liverpool player since John Barnes in 1990 to claim the honour.
"I'm delighted but I'm a little bit surprised," said the 28-year-old. "When you look at the quality of the players there are in this league, it's a great privilege to win this kind of award.
"The quality is getting better and better each year so to win this award is a great achievement for myself.
"Then further back players like Ian Callaghan and Terry McDermott who were heroes to my dad and so many other Liverpool fans."
Gerrard will receive the trophy at an Football Writers' Association gala dinner in London on May 29.
"I'm really pleased for Steven," Benitez told liverpoolfc.tv. "It is fantastic for him because he was competing with a lot of good players.
"For him to be named player of the year is massive credit to him and shows just how much he has achieved."