Dengue is the most medically important arthropod-borne viral disease, with 50-100 million cases reported annually worldwide. As no licensed vaccine or dedicated therapy exists for dengue, the most promising strategies to control the disease involve targeting the predominant mosquito vector, Aedes aegypti. However, the current methods to do this are inadequate. Various approaches involving genetically engineered mosquitoes have been proposed, including the release of transgenic sterile males. However, the ability of laboratory-reared, engineered male mosquitoes to effectively compete with wild males in terms of finding and mating with wild females, which is critical to the success of these strategies, has remained untested. We report data from the first open-field trial involving a strain of engineered mosquito. We demonstrated that genetically modified male mosquitoes, released across 10 hectares for a 4-week period, mated successfully with wild females and fertilized their eggs. These findings suggest the feasibility of this technology to control dengue by suppressing field populations of A. aegypti.