Is Metal Gear Solid the first game in the Metal Gear series?

In KONAMI's official introduction, the 1987 MSX2 game Metal Gear is described as the starting point of everything. The 1990 MSX2 game Metal Gear 2: Solid Snake is listed as the sequel to the original, and also belongs to the series history before Metal Gear Solid.

The About page for Metal Gear Solid explicitly states: the 1998 PlayStation game Metal Gear Solid is the third entry in the Metal Gear series, and it introduced real-time fully polygonal presentation, achieving complete 3D. The official Legacy Collection timeline also calls it the third canonical entry in the series.

So, if the question is whether Metal Gear Solid is the first game in the series, the answer is no. There are two canonical entries before it, and the second one already had Solid Snake in its title.

Laying out the three games by release date makes the relationship clearer. The title jumping from Metal Gear 2 to Metal Gear Solid does not mean the series restarted from the first entry.

Metal Gear Solid's "first" lies in its presentation: it was the series' first real-time fully polygonal, fully 3D game. It was not the first time Solid Snake appeared in the series, nor the first time stealth design was used. The original Metal Gear had already established the core of avoiding direct combat and infiltrating enemy territory, the second game's title already included Solid Snake, and Metal Gear Solid placed all of that into the fully 3D Shadow Moses island.

KONAMI's Introduction page calls it the first fully 3D game in the series, released in 1998, with the story set on Shadow Moses island and the protagonist being Solid Snake. So treating it as the "starting point of 3D" is reasonable, but treating it as the starting point of the entire series is wrong.

The misunderstanding mainly comes from several aspects. First, the title has no number 3 and is simply called Metal Gear Solid, which looks like a fresh start. Second, the 1998 game gained immense popularity on PlayStation, and many people first encountered the series through this entry. Third, the full 3D transition brought a strong sense of a new generation, further reinforcing the impression of a "new beginning."

However, none of this proves that KONAMI intended to make it the first game in the series. Current official materials establish the order of the games and their technical presentation, but not the naming motive; those pages alone cannot explain why Solid replaced a number in 1998.

Depending on your focus, the entry point can vary.