Is the Master Ball Missable in Pokemon FireRed?

No. The Master Ball in Pokemon FireRed is not missable due to story progression.

It is given by the President of Silph Co after defeating Giovanni during the Silph Co incident.

Even if you leave the building and return later, the President will still give you the Master Ball as long as you have not already received it.

The same rule applies in Pokemon LeafGreen.

Why This Moment Feels Uncertain#

Silph Co is a major story event and part of the limited rewards and one-time items in Pokemon FireRed that players may worry about missing.

It includes:

Multiple floors of battles
A boss fight against Giovanni
A rescue scene with the company president

Because the story advances quickly after Giovanni is defeated, some players worry that leaving the building or progressing the story might cause the reward to disappear.

The game does not explicitly clarify whether this gift is tied to a limited event window.

What Actually Happens#

In Pokemon FireRed:

The Master Ball is given by the Silph Co President after Giovanni is defeated.
The NPC remains in the office after the event.
The reward does not expire.
You can return later to receive it if you have not already accepted it.

What This Does NOT Affect#

Receiving the Master Ball does not:

Lock any Gym
Block story progression
Create a dead end

The item is extremely powerful, but it is not required to complete the main storyline.

If you are wondering about quantity limits, see whether you can get more than one Master Ball in Pokemon FireRed.

In Short#

The Master Ball in Pokemon FireRed is not missable due to story progression.

The Silph Co President will continue to offer the item even if you return later.

However, the gift can only be received once per save file.