Diwani is a calligraphic variety of Arabic script, a cursive style developed during the reign of the early Ottoman Turks (16th century - early 17th century). It was invented by Housam Roumi and reached its height of popularity under Süleyman I the Magnificent (1520–1566).
It was labeled the Diwani script because it was used in the Ottoman diwan and was one of the secrets of the sultan's palace. The rules of this script were not known to everyone, but confined to its masters and a few bright students. It was used in the writing of all royal decrees, endowments, and resolutions.