JIRA, Redmine, OpenProject, YouTrack, Eventum, Bugzilla, not8, Timeline.io, Request Tracker, Tuleap, Eclipse Mylyn, jtrac, ProjeQtOr, FogBugz, Flyspray, The Bug Genie, uBugtrack, Allegra, Lavagna, Plutio, NodePoint, Bontq, JobNimbus, Acunote, BugTower, Codendi, Vermis, Zoho BugTracker, Bugira, Retrospectiva, Pivotal Tracker, Lean Testing, XBtrack task and bug tracker, IssueBurner, Jixee, SPECZ.io, Akiri DevBox, ChiliProject are some alternatives to Mantis Bug Tracker.