Who wrote Deuteronomy:

Deuteronomy, the last book of the Pentateuch (Genesis, Exodus, Leviticus, Numbers, and Deuteronomy), is believed to have been written by Moses. According to Jewish and Christian tradition, Moses wrote the Pentateuch during the Exodus from Egypt.

Most scholars believe additions were made to the Pentateuch following the death of Moses, such as the account of Moses’ death. Many Christian scholars agree with this assumption. However, while Moses may not have been the author of the entire pentateuch, he is considered by most to be the author of the majority of the Pentateuch. If one person were to be identified as the author of Deuteronomy and the Pentateuch, most scholars would agree it would be Moses.