The Urim and Thummim (typically translated as "light" and "perfection") was a sacred lot used by ancient Hebrews (ususally Israelites) to determine God's will or God's answer to a particular question. Some believe that questions were asked with only two possible answers, and the Urim and Thummim provided the answer. The earliest reference to them in the Bible is that Aaron, Moses' brother, carried them with him as High Priest. Many scholars believe they were stones that resided in the breastplate (with other precious stones) of the Jewish High Priest ceremonial clothing when he officiated in the tabernacle or temple. The most recent reference to a Urim and Thummim in the Bible (depending on translation) is the replacement of Judas as an Apostle by St. Mathias in the Acts of the New Testament. Scholars are unconclusive if the relics are the same or different objects.

Mormons claim that Joseph Smith, Jr had a urim and thummim which he used at first to translate the Book of Mormon from gold plates until he had learned the language on the plates well enough to translate them alone by revelation. Mormons also claim that Smith dictated some of the sections of the Doctrine and Covenants (in answer to various questions asked of God) by means of revelation from the urim and thummim and that they were also used to facilitate some portions of the Joseph Smith Translation of the Bible.

Masonic Legend (taught during the 13, 14 and 21 degrees ceremonies of Masonry) and Kabbalistic tradition states that the Urim and Thummin was part of the recovered artifacts taken from Solomon's Temple after Hiram Abif was murdered while protecting the temple treasury. According to the legend, the Urim and Thummin and other recovered treasure was placed back in the temple treasury.