There are at least twelve artists/groups using this name.
1) Rapper from Australia who released the album Power Of The Spoken.
2) darkwave band Mantra was based in Manchester, UK from 1997-2001. Core members included: Simon Carroll on guitars; Yvonne Neve, performing vocals and keyboards and Phil Wallis on bass. They produced two albums, Every Defect and Painted Red. Lately, former band members Simon Carroll and Yvonne Neve formed the two piece Red Painted Red. http://www.myspace.com/redpaintedred.
3) Experimental electronic pop band from Reading, Pennsylvania.
4) The fourth band called Mantra is a 1981 funk band produced by Larry Blackmon and Anthony Lockett from legendary funk band Cameo. The band's leader Roger Harris later appeared in another Blackmon produced project, Cashflow, before joining the Manhattans in the late 80s. Mantra released one self titled album in 1981, Mantra.
5) The fifth band called Mantra is an Italian hard rock formation. In 2004 they released Hard Times which credited: Jacopo Meille (Tygers Of Pan Tang) vocals, Matt Giuliani backing vocals, Gianluca Galli (Time Machine) guitars, and Senio Firmati on Drums, Percussion.
6) Indonesian band. Members are: Anda "Bunga," Khaseli "Zeke" Gumelar, and Emil "Naif."
7) Reggae artist form Argentina, Pablo Beltrán.
8) a Jazz Rock band featuring Michael Roberts guitar, Alex Magor keyboards, Evan Joyce bass, and Erik Egol drums, that serve up an eclectic mix of sounds, from slamming funk to progressive metal, classical inspired arrangements, and sizzling uptempo jazz fusion. http://www.moremantra.com
9) The ninth band called Mantra is a Hungarian (krishna) metal band. http://www.mantra.hu/
10) Mantra is a producer from the Virgin Islands, specifically St. Croix. He is a member of the WYSF Collective and has been making experimental hip hop and electronic music for years. www.wysf.bandcamp.com
11) Stoner rock band from Viana do Castelo, Portugal.
12) Hard rock band from York, UK consisting of Oli Stevens-Vallecillo: Guitar & Vocals
Catherine Redfern: Guitar & Backing Vocals and James Fletcher: Bass. https://soundcloud.com/mantra_uk