Who wrote Joshua in the Bible?

Answer 1

Based on internal evidence and tradition, Joshua himself wrote much of the book except for, of course, the account of his death and several accounts later added to it. Joshua 24 records that Joshua wrote the words that were added to Moses' books of law:

25 So Joshua made a covenant with the people that day, and set them a statute and an ordinance in Shechem. 26 And Joshua wrote these words in the book of the law of God, and took a great stone, and set it up there under an oak, that was by the sanctuary of the LORD. 27And Joshua said unto all the people, Behold, this stone shall be a witness unto us; for it hath heard all the words of the LORD which he spake unto us: it shall be therefore a witness unto you, lest ye deny your God.

Answer 2

Approximately eighty per cent of scholars are said to agree that that the Conquest of the Land did not take place as described in Joshua, so there is a near-consensus that the book could not have been written as an accurate history by a participant in that history.

A substantial majority of biblical scholars say that the Book of Joshua was written by the 'D' (Deuteronomist) source. They say that it is part of the Deuteronomic history, which includes the Books of Joshua, Judges, 1 and 2 Samuel and 1 and 2 Kings, and covers the assumed conquest of Canaan through to the end of the kingdom of Judah and the beginning of the Babylonian Exile. Not only do these books form a closely integrated block of text, but they were all written in the same style and in a more modern form of Hebrew that would be anachronistic for the time attributed to Joshua.