Hanuman - 11th Rudra of Lord Shiva

Shiva has eleven forms of Rudra. He has several names and avataras and various scriptures and religious books give different names. However the 11 Rudras worshipped in the Ekadasa Rudrabhishekam Pooja is the most reliable information. 

The 11 Rudras are as follows: 
1. Mahadeva, 
2. Shiva , 
3. Maha Rudra, 
4. Shankara, 
5. Neelalohita, 
6. Eshana Rudra, 
7. Vijaya Rudra, 
8. Bheema Rudra, 
9. Devadeva, 
10. Bhavodbhava and 
11. Adityatmaka Srirudra. 

Their 11 consorts of these 11 Rudras are: 
1. Dhee devi, 
2. Dhritti devi, 
3. Ushna (Rasala) devi, 
4. Uma devi, 
5. Neeyut devi, 
6. Sarpi devi, 
7. Eela devi, 
8. Ambika devi, 
9. Ieravati devi, 
10. Sudha devi and 
11. Deeksha devi respectively. 

The 11 Rudras that form Ekadasa Rudra manifest at the time of the destruction of the material universe to burn it down and destroy it. They are: 
1. Kapali 
2. Pingala 
3. Bhima 
4. Virupaksha 
5. Vilohita 
6. Shashta 
7. Ajapada 
8. Ahirbidhanya 
9. Sambhu 
10. Chanda 
11. Bhava 

Hanuman is mentioned as an avatar of Shiva or Rudra in the Sanskrit texts like Mahabhagvata Purana, Skanda Purana, Brhaddharma Purana and Mahanataka among others. It is believed that Panchamukha Hanuman is the 11th rudra of Lord Shiva. 

Jai Sri Ram