Prasannanjaneya is an incarnation of Hanuman. Parashara Agama Samhita text mentions about the nine avatars of Hanuman. In that the first avatar is that of Prasanna Anjaneya. As per the Parashara Agama Samhita, Hanuman as the devotee of Sri Ram is the ninth incarnation.
The concept of Prasanna Anjaneya murti is more popular in Andhra Pradesh.
This incarnation of Hanuman is a pleasant form.
There is a popular belief that worship of Prasannanjaneya murti helps in solving issues related to children. Those couples who have no children are blessed with children after worship of Prasanna Anjaneya. Health of the children also improves after Prasannanjaneya worship.
Most popular temples dedicated to Prasannanjaneya are found in Andhra Pradesh. Today, most temples offer worship to Prasannanjaneya as a devotee of Sri Ram. It is Hanuman based on Ramayana that is worshiped as Prasannanjaneya. Parashara Agama Samhita is today purely followed for performing pujas and vrats.