Saint John Climacus (ca. 579 - 649), also known as John of the Ladder, John Scholasticus, and John Sinaites, was a seventh century monk at St. Catherine's monastery on Mount Sinai. The Orthodox Church celebrates his feast day on March 30.
He came to the monastery and became a novice when he was about 16 years old, and when he died in 649 he was the monastery's abbot. He wrote a number of instructive books, the most famous of which is The Ladder of Divine Ascent. (It is because of this book that John is known as "Climacus," which means "of the ladder".) It describes how to raise one's soul to God, as if on a ladder. This book is one of the most widely read among Eastern Orthodox Christians, especially during the season of Great Lent which immediately precedes Pascha (Easter), and on the fourth Sunday of Great Lent he is especially commemorated.