Mercury-Redstone BD was an unmanned booster development flight in the U.S. Mercury Programme. It was launched on March 24, 1961 from Launch Complex 5 at Cape Canaveral, Florida. The mission used a boilerplate Mercury spacecraft and Redstone MRLV-5.

After the problems that developed during the MR-2 mission carrying the chimpanzee Ham, it was apparent that the REedstone needed further development before it could be trusted to carry a human passenger.

Dr. Wernher von Braun added Mercury-Redstone BD to the launch schedule between the MR-2 and MR-3 missions.
The cause of previous Redstone rocket over-accelerations was a servo valve that did not properly regulate the flow of hydrogen peroxide to the steam generator. This in turn overpowered the fuel pumps. The thrust regulator and velocity integrator were modified on the MR-BD and later Mercury-Redstone rockets to prevent them from exceeding the speed limit again.

Another problem encountered in previous Mercury-Redstone flights were harmonic vibrations induced by aerodynamic stress in the topmost section of the elongated Redstone. To fix this problem, four stiffeners were added to the ballast section and 210 pounds (95 kg) of insulation was applied to the inner skin of the upper part of the Mercury Redstone instrument compartment.
The mission used a boilerplate Mercury spacecraft, with inert escape rocket. The spacecraft also did not have a retro package or posigrade rockets.

The MR-BD mission lasted eight minutes and 23 seconds. It reached an apogee of 113.5 miles (183 km) and a range of 307 miles (494 km). The peak velocity was 5,123 mph (8,245 km/h). The spacecraft experienced a peak load of 11 g (108 m/s²). There was no intention to separate the Redstone rocket and boilerplate Mercury spacecraft and they impacted together 307 miles (494 km) downrange, five miles (8 km) short of the plan. They sank to the bottom of the Atlantic Ocean, exploding a sofar bomb en route.

MR-BD was highly successful and led the way to the flight of Alan Shepard aboard MR-3.