John Mark
John Mark is named in the Acts of the Apostles as an assistant accompanying Paul and Barnabas on their missionary journeys. Traditionally he is regarded as identical with Mark the Evangelist.
Biblical account
Several times the Acts of the Apostles mentions a certain "John, who was also called Mark" or simply "John":
And Barnabas and Saul returned from Jerusalem when they had fulfilled their mission, bringing with them John whose other name was Mark.
When they arrived at Salamis, they proclaimed the word of God in the synagogues of the Jews. And they had John to assist them.
Now Paul and his company set sail from Paphos, and came to Perga in Pamphylia. And John left them and returned to Jerusalem; but they passed on from Perga and came to Antioch of Pisidia.
And Barnabas wanted to take with them John called Mark. But Paul thought best not to take with them one who had withdrawn from them in Pamphylia, and had not gone with them to the work. And there arose a sharp contention, so that they separated from each other; Barnabas took Mark with him and sailed away to Cyprus, but Paul chose Silas and departed, being commended by the brethren to the grace of the Lord.