The Main Deck is the central area of the Biologic Space Laboratories research station.
The Main Deck is where the Habitation Deck, Operations Deck, Reactor Silo, and Docking Bays are located. Ridley's clone from Metroid: Other M is frozen and preserved in the Sub-Zero Containment room. The Restricted Zone is also included on the map, classifying it as another sub-area of the Main Deck.
The Main Elevator leads to Elevators 1-6, which in turn lead to each of the station's six sectors. This functionally makes the Main Deck the "hub area" of the BSL station, since any other area can be accessed from the Main Deck.
Samus Aran begins and ends her mission in the Main Deck, arriving in the Docking Bays in her new Starship. After determining that the X Parasites had escaped the Quarantine Bay and started infecting all other bioforms on the station, Samus battles Arachnus and heads to Sector 1 (SRX) as the SA-X continues to create damage. She visits the Habitation Deck to check for survivors: the Etecoons and Dachoras from Zebes. When the station loses power due to Nettori's vegetation, Samus navigates the ventilation shafts of the Main Deck and restores power in the Reactor Silo's Auxiliary Power Station. Samus and the SA-X discover the Restricted Laboratory, and the Restricted Zone is subsequently jettisoned from the station. To prevent the Galactic Federation from weaponizing the X, Samus plots a course of impact with SR388 in the Operations Room and finally evacuates through the Docking Bay, battling the SA-X and Omega Metroid along the way.
- 3 Energy Tanks
- 7 Missile Tanks
- 3 Power Bomb Tanks
- Missile Launcher
- Morph Ball
- Space Jump
- Ice Beam
- Unnamed Suit
- Core-X (Arachnus/Neo-Ridley/SA-X)
- Dachora (Habitation Deck, non-hostile)
- Etecoon (Habitation Deck, non-hostile)
- Neo-Ridley (X Parasite escapes Ridley corpse)
- Omega Metroid
- Ridley (frozen in Sub-Zero Containment)
- X Parasite
- Zombie researcher
"This area contains elevator access, storage, etc."
The music theme that plays in this area is almost always different every time Samus visits it. On many occasions, Facing a Huge Reaction is heard. When Samus first enters the Main Deck, Environment Sound (Tension) is heard. In some cases, usually to foreshadow a bad event that will occur, the BGM will not play at all. In the endgame, Last Instructions play throughout the Main Deck, followed by Escape during the final countdown sequence.