John, the author of the Gospel of John, as indicated by this book's comparable style and tone.
Time of Writing:
Approximately A.D. 90—95, after John's return from exile on Patmos, according to church history and the content of this book.
Place of Writing:
Ephesus, where, according to church history, John ministered in his last days.
The believers in general, who have the eternal life of God by believing into the Son of God (5:11-13