Rebel

Rebels are any group that wants to break away from a primary government. "Rebel" may refer to...

In the UNSC
 * Frieden Rebels, a secessionist faction that fought against the UN in the Interplanetary War


 * Koslovic Rebels, the neo-Communist faction that fought against the UN in the Interplanetary War


 * Eridanus Rebels, the faction of human rebels in the Eridanus System


 * United Rebel Front, the larger faction of human rebels united against the UNSC government.

In the Covenant
 * The Heretics, the breakaway faction that follows Sesa 'Refumee and is against the Great Journey.