It appears to have been Irish monks in the 7th and 8th century who introduced spaces between words in religious texts https://www.sup.org/books/title/?id=683 h

It appears to have been Irish monks in the 7th and 8th century who introduced spaces between words in religious texts https://www.sup.org/books/title/?id=683 https://www.sup.org/books/title/?id=683