The former Guns N' Roses star saw off competition from Soundgarden's Kim Thayil and Jim Root of Slipknot to take the crown in the online magazine's reader vote.
Meanwhile, singer Myles Kennedy, who fronts Slash's solo work, was named Vocalist of the Year, triumphing over runner-up Corey Taylor of Slipknot and Soundgarden star Chris Cornell.
Slash was thrilled with the honour, writing in a post on Twitter: "Just found out that Myles and I won the Loudwire poll! I'm stunned. Thanks so much to all of you who voted! Just talking to Myles; we can't get over the avalanche of votes you must have sent in for us to win the Loudwire deal. Cheers!"
Marilyn Manson bagged Rock Video of the Year for No Reflection, Three Days Grace's won Rock Song of the Year for Chalk Outline, Black Sabbath guitarist Tony Iommi was voted Rock Titan of the Year, Motley Crue's Nikki Sixx was best bassist and Vinnie Paul of Pantera landed the top drummer mention.