The RepRap project is an initiative to develop a 3D printer that can print most of its own components. RepRap (short for replicating rapid prototyper) uses a variant of fused deposition modeling, an additive manufacturing technique. The project calls it Fused Filament Fabrication (FFF) to avoid trademark issues around the "fused deposition modeling" term.

As an open design, all of the designs produced by the project are released under a free software license, the GNU General Public License.