How many people in Bible did God name before birth?

Solomon Josiah Issac Cyrus

Another Answer:

These four were known before their births and God sanctified them for a special purpose: Jeremiah, John the Baptist, Jesus Christ and the apostle Paul (Jeremiah 1:1-5; Luke 1:13-14; Isaiah 49:1, 5; Galatians 1:15).

God instructed Hagar to name her soon to arrive son Ishmael for a specific reason (Genesis 16:11).

The same with Sarah naming her son Isaac due to Abraham and Sarah's laughing (Genesis 17:19).

In the Old Testament, names had meanings. Pharaoh's sister, a Princess named Moses meaning "drawn out," because she "drew him out of the water" (see Exodus 2:10).

2 Samuel 12:24-25

New King James Version (NKJV)

Solomon Is Born

24 Then David comforted Bathsheba his wife, and went in to her and lay with her. So she bore a son, and he[a] called his name Solomon. Now the Lord loved him, 25 and He sent Word by the hand of Nathan the prophet: So he called his name Jedidiah, because of the Lord.

Lastly, God spoke of two future people who would come to do His will: Josiah (1 Kings 3:2) and Cyrus (see Isaiah 44 and 45).