Williams joined NME as a freelancer, before being appointed features editor in September 2010 and deputy editor in June 2011, working across NME's multiple platforms.
Murison announced last month that she will step down to join The Sunday Times in June.
She had joined NME in 2003 as a staff writer, but became the first female editor of the magazine in July 2009 after the departure of Conor McNicholas.
Prior to joining NME, Williams was the launch editor of Kruger magazine and helped guide it from a small Cardiff fanzine to a high-quality, national music title.
"I'm super excited to be the new editor of NME. As far as dream positions go, it really doesn't get any better than this," he said.
"Krissi Murison has done an amazing job as my predecessor, and I'm totally honoured to pick up the baton from her.
"My challenge is to make NME magazine and the wider NME brand even sharper, our message more coherent and to engage even more with NME's audience of passionate music fans. With the brilliant team we've got in place, I can't wait to get started!"
IPC publishing director Emily Hutchings added: "After an extensive recruitment process, I am absolutely thrilled to announce Mike Williams as the next editor of NME.
"He brings with him a wealth of editorial experience as well as knowledge in managing multiplatform brand extensions. Mike demonstrated a clear strategic vision and passion for NME that will help take the brand on to even greater success."