A Morph Ball Door is a special door in the Prime Series. These doors open automatically when Samus approaches them in Morph Ball form. Sometimes they will open up into tunnels that will suck Samus in, such as in a Waste Disposal Unit in the Phazon Mines. Most of these can be found in Space Pirate areas such as the Mines, the Agon Wastes mining facility and on the Pirate Homeworld. In Metroid Prime Hunters these are identified as normal Doors, retaining their function and the ability to be opened with weapons fire.
- Main Plaza
- Energy Core
- Burn Dome Access
- Crossway Access West
- Training Chamber
- Piston Tunnel
- Quarantine Cave
- Quarantine Monitor
- Life Grove Tunnel
- Life Grove
- Security Cave
- Phendrana's Edge
- Waste Disposal
There are at least two specially named Morph Ball Doors on SkyTown, Elysia.
The first, called the maintenance level hatch, exists in the Aurora Chamber to the right of the corrupted Aurora Unit 217. When Samus attempts to interface with 217, the "SkyTown announcer" states that 217 is corrupted and requires repair, and opens the hatch. This hatch is primarily brown in color with a lighter amber border, and has a "target" symbol on it with a turquoise center. The hatch splits vertically from the middle and remains open.
The second, called an entry lock, is present in the upper chamber of the Powerworks. This hatch is locked at first, and must be removed by firing Seeker Missiles at locking mechanisms attached to an energy grid. This will lift the hatch and allow Samus to access the Spider Ball.
- "Entry lock active. Connections to energy grid are present."
- The inclusion of these Doors was apparently made after the first Prime game ran into issues whilst testing. Testers would travel too quickly through the Morph Ball tunnels and as a result, fall off the map. 
- ^ [Metroid Prime :: Speed Run in 1:24:31 by Miles #AGDQ 2014] Sub-sub-sub-sub-hour run. Zoid. Retrieved on 2015-02-28.