I have always seen references to Brahma of 4 faces (caturmukha Brahma).
There is a story of Siva cutting off one of Brahma's heads - which means that he must have been pancamukha (5-headed) before that.
Does scripture support this?
note: this is not a duplicate of
Why did lord Shiva chop off lord Brahma's fifth head?
it only asks - do scriptures say Brahma originally started off with five faces.
Lord Brahma having five faces is mentioned in various Puranas. However, the story of how he eventually lost the fifth head is being (apparently) told in different ways in the different Puarnas.
Here is a reference from the Brahma Purana:
Brahma’s Head
Years ago, there was a war between the gods and the demons and the gods came to Brahma for advice and Brahma asked them to pray to Shiva.
When Shiva appeared before them, the gods said, The demons have defeated us. Please kill them and save us.
Shiva went to fight with the demons. He drove the demons off from Mount Sumeru and out of heaven. He pursued them to the ends of the earth. All this exertion made Shiva sweat. And wherever the drops of sweat fell down on the ground, terrible ogresses named matris were created. The matris also started to kill the demons and pursued them down to the underworld.
While the matris were killing the demons in the underworld, Brahma and the other gods waited on the banks of the river Goutami Ganga. This place came to be known as Pratishthana.When the matris had killed all the demons, they returned to earth and began to live on the banks of the Goutami Ganga. This tirtha has come to be known as matritirtha.
Brahma used to have five heads. The fifth head was in the shape of a donkey’s head. When the demons were running away to the underworld, this donkey’s head addressed the demons and said, Why are you running away? Come back and fight with the gods. I shall aid you in your fight.
The gods were alarmed at this paradoxical situation. Brahma was helping them in their fight with the demons and Brahma’s fifth head was trying to help the demons. They went to Vishnu and said, Please cut off Brahma’s fifth head. It is causing too much of confusion.
I can do what you want, replied Vishnu, but there is a problem. When the cut-off head falls on earth, it will destroy the earth. I think you should pray to Shiva to find a way out.
The gods prayed to Shiva and Shiva agreed to cut off the head. But what was to be done with the severed head? The earth refused to bear it and so did the ocean. Finally it was decided that Shiva himself would bear the head.
And, here is a reference from Matsya Purana:
Shatarupa is also referred to as Savitri, Gayatri, Sarasvati or Brahmani. Since she had been born from Brahma’s body, she was like Brahma’s daughter. In fact, Vashishtha and the other sages who were Brahma’s sons welcomed her as their sister. But Shatarupa was so beautiful that Brahma fell in love with her and wished to marry her.
Shatarupa circled Brahma and showed her respects to him. When she stood in front of him. Brahma gazed upon her with the face that he had. But when she went and stood behind him, Brahma could see her no longer. (Brahma, obviously, did not want to turn his head.) Another head with another face therefore sprouted behind Brahma’s first head so that he might be able to see Shatarupa. In similar fashion, a head sprouted to Brahma’s first head so that he might be able to see Shatarpa. In similar fashion, a head sprouted to Brahma’s right an another one to his left. And when Shatarupa rose above him, a head sprouted towards the top as well. Thus it was that Brahma came to have five heads and five faces.
It is mentioned in Shiva Purana:
Mahadeva then created a wonderful person, Bhairava, from the middle of his brows to quell the pride of Brahma.
This Bhairava knelt before the lord in the battle-field and said "0 lord, what shall I do ? Please give me your directives quickly."
"Dear, here is Brahma, the first deity of the universe. Worship him with your sharp-pointed quick-moving sword."
With one of his hands he caught hold of the tuft of Brahma's fifth head that was guilty of haughtily uttering a falsehood, and with the hands he furiously shook his sword in order to cut it off.
(Vidyeshvarasamhita Chapter 8)
