Question: Who wrote the book of 1 and 2 thessalonians?
Disambiguated questions and answers: question: Who is traditionally said to have written 2 Thessalonians?
Who do many modern scholars argue wrote 2 Thessalonians?
Who do most scholars say wrote 1 Thessalonians?
answer: Paul the Apostle, with Timothy
not written by Paul but by an associate or disciple
Paul the Apostle
Natural Questions answer: Paul the Apostle (from the Wikipedia article "First Epistle to the Thessalonians")