Marek may be an eleventh-century bishop of Płock, Poland. He was mentioned by the chronicler Jan Długosz.[1]
Historian Wojciech Kętrzyński considered him as non-historical person, like his allegedly predecessors mentioned by Długosz.[1] Historical of Marek was still doubted by historians.[1] If he was a bishop of Płock, he was bishop since ca. 1075, where the diocese was erected.[1]
According to Jan Długosz, he died on 8 August 1087.[1] We do not know which was base for this information.[1]