Gemini X (space mission in Project Gemini)
July 18-21, 1966
John W. Young, Michael Collins
2 days, 22 hours, 46 min, 39 seconds

First use of Agena target vehicle's propulsion systems. Spacecraft also rendezvoused with Gemini VIII target vehicle. Collins had 49 minutes of EVA standing in the hatch and 39 minutes of EVA to retrieve experiment from Agena stage. 43 orbits completed.

Source: NASA