Not to be confused with the US release "Final Fantasy II", which is actually Final Fantasy IV
Canonically this is the second Final Fantasy game.
Neither Final Fantasy II or Final Fantasy III were initially released outside Japan, so Final Fantasy IV in North America was released as Final Fantasy II.
The US Final Fantasy releases were correctly numbered starting with the PSX releases.
The only U.S. releases of the true Final Fantasy II were on PlayStation and GBA.
From the game box:
The legend continues. A new evil threatens the land, and once more, a band of young heroes stands against it.
User summary:
Final Fantasy II was the second FF installment by Square. The game features a distinguishly darker "rebel army" scenario, and is infamous for its unique 'levelling' system – characters increased their HP by being wounded in battle, and players quickly realized that hitting yourself was the best way of getting wounded. Players ended up entering battle only to constantly hit themselves, attacking the real enemies only when they had lost enough HP to get a gain.
Individual credits:
Hironobu Sakaguchi: Director
Nobuo Uematsu: Music
Yoshitaka Amano: Character & monster design
Microbadges: