Are amphibians invertebrate or vertebrate animals?

No. Amphibians are not invertebrates. They have an internal skeleton including a backbone which makes them vertebrates.

The scientific classification of amphibians is:

• Kingdom: Animalia
• Phylum: Chordata
• Subphylum: Vertebrata
• Class: Amphibia

The largest phylum of invertebrates is Arthropoda, which includes insects.