Is principal masculine or feminine in French?

Le principal. "Principal" is masculine in French. Nouns ending in -al, -el, -il, -ol, or -eul are usually masculine.

Is principal masculine or feminine?

leprincipal

/lə pʁɛ̃sipal/masculinesomeone or something which is important

The feminine form is principale

Nouns ending in -al, -el, -il, -ol, or -eul are usually masculine.

The whole family: -al, -el, -il, -ol, -eul. All masculine.

96.5% of -al / -el / -il / -ol / -eul nouns are masculine

Toutes les principales cartes de crédit sont acceptées.
All major credit cards are accepted.
Le Japon se compose de quatre îles principales.
Japan consists of four main islands.
Sa maladie est une de ses principales inquiétudes.
His illness is one of her chief anxieties.