No, Corinthians is not in the Old Testament. The books of Corinthians are part of the New Testament in the Christian Bible. Specifically, there are two books: 1 Corinthians and 2 Corinthians. These books are letters written by the Apostle Paul to the church in Corinth. They address various issues within the early Christian community and provide guidance on how to live a Christian life.
The Old Testament, on the other hand, is the first part of the Christian Bible and is based primarily on the Hebrew Bible. It includes books like Genesis, Exodus, Psalms, and Isaiah, which were written before the time of Jesus Christ. The New Testament, which includes Corinthians, focuses on the life and teachings of Jesus and the early Christian church.