Space borders are borders between space-faring factions or territories. Like borders in general, these locations may be rigidly defined or may be more nebulous with borderlands, frontiers, neutral zones, and contested territory. Borders between space empires may contain space stations, outposts, satellites, and space minefields. Settlements at these locations may resemble border towns or frontier towns. Borders may be patrolled and if there is tension between the adjacent civilizations there may be war fleets located along the border in a show of force, as a deterrent, or engaged in open warfare.

Fictional space borders are most often depicted similarly to the more familiar borders found on a fictional planet. Conceptually this is easiest to imagine, easiest to design, and easiest for audiences to understand. However, designers should note that this perspective renders outer space in only two dimensions. True space borders would need to envelope three-dimensional space.

Space is big. When designing borders for space-faring civilizations, consider how those borders are maintained, monitored, and enforced. There may be new technologies that aid in this endeavor.