Hanuman chalisa is a collection of hymns ( strota) addressed to Lord Hanuman.It was authored by 16th century poet Tulsidas.It consists of forty chaupayees.There are three couplets two preceding and one proceeding this collection.It's written in Awadhi.

Hanuman Chalisa was written by Sant Kavi Tulsidas back in the 15th century. Saint Tulsidas was an ardent devotee of Lord Ram, and was eager to get a darshan of Lord Ram. In those days, he used to chant Ram naam and recite the Ramcharitmanas near the Varanasi ghat every day in the evening. Lots of people used to gather to listen to his chantings.

It was during this time that Saint Tulsidas got to know from someone, that Lord Hanuman himself attends his evenings chantings everyday, and if he prays to Lord Hanuman, he can get a darshan of Lord Rama. Tulsidas got to know that Hanuman ji disguises himself in the form of an ugly looking old person, and that he is the first person to arrive, and the last one to leave.

Now, Saint Tulsidas made sure to meet Lord Hanuman on the next evening, and pray to him for Lord Ram’s darshan. The next day, Tulsidas was able to recognize Hanuman ji, and after the session was over, he starts following Lord Hanuman (who was in disguised form). Once he meets Hanuman ji, Tulsidas immediately falls into his feet. It was then, when he composed Hanuman Chalisa to please Lord Hanuman. Lord Hanuman being satisfied with his devotion, reveals his true identity to Tulsidas, and grants him with the boon to get a darshan of Lord Ram.