Who wrote the first thesuarus?

The first thesaurus, in the sense of a book specifically dedicated to synonyms and antonyms, is generally attributed to Peter Mark Roget. He published the first edition of his "Thesaurus of English Words and Phrases" in 1852.

However, it's worth noting that the concept of a thesaurus existed long before Roget. Ancient Greek and Roman scholars created lists of synonyms and related words, and there were attempts at compiling thesauri in the 18th century.

Roget's contribution was the development of a systematic and comprehensive approach to organizing words based on their relationships, which made his thesaurus a landmark publication and a foundation for future thesauri.