Abolfazl Beyhaghi (995-1077; Abd ul-Fazl Mohammad Ibn Hossein Beyhaği) was an Iranian historian and author. He wrote the Tarikh-e Mas'oudi (Masoudian History) (other name: Tarikh-e Beyhaghi.)

Beyhaghi was born in the village Haares-Abad of Beyhagh in Khorasan Province. He studied various sciences in Neishabur city, and then he was employed as a clerk in the Secretariat of King Mahmud. Abolfazl could show his efficiency there.

In 1039 his master and chief Bu-Nasr Moshkan passed and a few years later King Abd ul-Rashid elected him as the chief of the Royal Secretariat.

After the retirement in 1058, Beyhaghi started the editing of his daily notes and historical data and published them in a book, named it "Tarikh-e Mas'oudi".

His book is one the most creditable sources about the Ghaznavid Empire, and his fluent prose style has made the book considerable in Persian literature too.