Apostle
In the Latter Day Saint movement, an apostle is a "special witness of the name of Jesus Christ who is sent to teach the principles of salvation to others." In many Latter Day Saint churches, an apostle is a priesthood office of high authority within the church hierarchy. As of March 31st, 2018, the Twelve Apostles of the LDS Church are: M. Russell Ballard, Jeffrey R. Holland, Dieter F. Uchtdorf, David A. Bednar, Quentin L. Cook, D. Todd Christofferson, Neil L. Anderson, Ronald A. Rasband, Gary E. Stevenson, Dale G. Renlund, Gerrit W. Gong, and Ulisses Soares. There are also members of the Quorum of the Seventy (referred to as “Seventies”). They typically work under the direction of the twelve apostles and are given similar responsibilities that build up the church. In many churches, apostles may be members of the Quorum of the Twelve Apostles of the church. In most Latter Day Saint churches, modern-day apostles are considered to have the same status and authority as the biblical apostles. In the Latter Day Saint tradition, apostles and prophets are believed to be the foundation of the church, with Jesus as the chief cornerstone. The Articles of Faith, written by Joseph Smith, mentions apostles: "We believe in the same organization that existed in the Primitive Church, namely, apostles, prophets, pastors, teachers, evangelists, and so forth."
Saint Matthias
There is no mention of a Matthias among the lists of disciples or followers of Jesus in the three synoptic gospels, but according to "Acts", he had been with Jesus from his baptism by John until his Ascension. In the days following, Peter proposed that the assembled disciples, who numbered about one hundred-twenty, nominate two men to replace Judas. They chose Joseph called Barsabas (whose surname was Justus) and Matthias. Then they prayed, "Thou, Lord, which knowest the hearts of all "[men]", shew whether of these two thou hast chosen, That he may take part of this ministry and apostleship, from which Judas by transgression fell, that he might go to his own place." Then they cast lots, and the lot fell to Matthias; so he was numbered with the eleven apostles.