Surak was a legendary Vulcan philosopher, scientist, and logician, considered the greatest of all who ever lived on Vulcan and the father of the modern Vulcan civilization. (TOS: "The Savage Curtain")
Surak lived in the 4th century, during the Time of Awakening. (ENT: "The Forge") As a scientist, he was considered on the same level as Albert Einstein and Isaac Newton. (Star Trek II: The Wrath of Khan)
Surak walked in Vulcan's Forge, beginning in the Gateway and crossing the Plain of Blood. His logic was said to have cooled it from the heat of battle. It was here that he founded the T'Karath Sanctuary. (ENT: "The Forge")
During the Time of Awakening, Vulcan suffered from a series of devastating wars, which nearly destroyed the planet. In the early stages of what was to be another devastating war, Surak's followers sent emissaries to propose peace. Many of these emissaries were killed, but over time they achieved peace on their planet. (TOS: "The Savage Curtain")
Surak was killed in the last battle against "those who marched beneath the Raptor's wings." (ENT: "The Forge") He died from radiation sickness caused by atomic weapons on Mount Seleya. (ENT: "Awakening")
Just prior to his death, Surak's katra was taken and housed in a katric ark. This ark was discovered in 2137 by Syrran, who became the holder of Surak's katra. With Surak's katra, Syrran founded the Syrrannite movement. (ENT: "The Forge")
Archer began having visions of Surak's time, and was able to find the T'Karath Sanctuary, the Kir'Shara, and identify the unnamed remains of T'Klaas. An attempt was made by T'Pau to remove Surak's katra from Archer, but it failed, as Surak wished to remain within Archer. (ENT: "Awakening")
Surak's original writings (the "Kir'Shara") were believed to no longer exist by the 22nd century, although his followers made copies of his teachings. (ENT: "The Forge") These teachings led to the majority of Vulcans purging their emotions. (ENT: "The Andorian Incident") The Teachings of Surak were translated into English by Skon prior to 2152. (ENT: "Two Days and Two Nights")
As the Kir'Shara was lost after Surak's time, his true teachings were largely forgotten by the mainstream Vulcan society by the 22nd century, resulting in many considering it a myth, while several radical sects claimed to follow his "real" teachings. (ENT: "Kir'Shara") A group of Vulcans, for example, known as the V'tosh ka'tur, examined these writings, and believed that Surak wanted Vulcans to master their emotions, not purge them. Revering him, the V'tosh ka'tur carried a small statue of Surak aboard the Vulcan civilian transport ship Vahklas. (ENT: "Fusion") Another of these sects was the Syrranites.
In 2285, David Marcus believed that, if Project Genesis had worked, his mother, Carol Marcus, would be remembered in the same breath as Isaac Newton, Albert Einstein, and Surak. (Star Trek II: The Wrath of Khan)
Surak was portrayed by actor Bruce Gray.
The introduction of Surak, through the appearance of the Excalbian image of the character, in "The Savage Curtain" intrigued many Star Trek fans and consequently generated a massive amount of fan mail, generally from viewers who demanded to see more of the character. (The World of Star Trek, 3rd ed., p. 146) Surak proved to be such an intriguing character that he and his philosophy remained popular subjects of conversation among fans for decades after the episode first aired. (Star Trek: The Original Series 365, p. 340)
In a letter to the editors of the fanzine Eridani Triad, which was dedicated to stories of Surak and the pre-Reform era, Barry Atwater stated that he had been "turned on" by the idea of Surak and commented, "I had to fight with the director and the two lead actors in order to play Surak the way I wanted to." (Barry Atwater, letter to the editors, facsimile printed in Eridani Triad 2 (Doris Beetem and Judith Brownlee, eds.), March 1971.)
In a memo from Gene Roddenberry to Harve Bennett (dated 1 August 1983), Roddenberry proposed there might be an "old legend" about the creation of Surak, from Vulcan's distant past, and that it might be established in Star Trek III: The Search for Spock. Surak, according to the backstory Roddenberry suggested, was essentially a composite Vulcan, resulting from a merge between the consciousness of a legendary, elderly Vulcan mystic and the body of a young, half-Vulcan priesthood acolyte. Before the joining, the Vulcan mystic had been "deep in mindmeld with another Vulcan" when a lightning bolt had struck the mystic with a lethal blow, and the same lightning bolt had glanced off the young acolyte, rendering him "mindless" but with his body intact. The merging (which had taken place on Mount Seleya) enabled "the mystic to live on for still another full lifetime, growing in wisdom until he became the Great Surak who laid the groundwork for Vulcan turning from emotion and violence to its present practice of logic." At the same time, a prophecy was made that the same fate would befall another Vulcan in the future, to the further benefit of Vulcan. Roddenberry proposed this backstory as a way of explaining why Vulcans, who had heretofore been portrayed as having a highly logical society, were extremely interested in a ceremony reuniting Spock's mind and body (on Mount Seleya), in the film's final draft script (and in the movie itself). Additionally, Roddenberry pointed out that, although most Vulcans didn't believe the prophecy, "yet the Great Surak is so revered for turning them from emotional savagery and showing them the way to logic that they can hardly ignore anything connected with him."
In a script written by Eric Stillwell for the third season of TNG, Surak would have been killed due to the accidental interference of a Vulcan science team which had used the Guardian of Forever to observe their past. As a consequence, the Vulcans never embraced logic and evolved into a race more like the Romulans, fighting a war with what was left of the Federation in the 24th century – however, the timeline was restored when Sarek, aboard the USS Enterprise-D to greet the returning scientists, went back to the Time of Awakening to take Surak's place. While the basic story – joined with one written by Trent Christopher Ganino, involving the reappearance of the "lost" USS Enterprise-C – became "Yesterday's Enterprise", the aired version removed the Vulcan plot entirely, showing a war with the Klingons instead. (Star Trek: The Next Generation Companion, 2nd ed., pp. 116-117)
The set dressing of a large wall sculpture depicting a face which was specifically created for the episode "The Andorian Incident" was suspected to be Surak's face, according to Michael and Denise Okuda. ("The Andorian Incident", text commentary, ENT Season 1 DVD special feature)
The statue of Surak in "Fusion" was designed by illustrator Doug Drexler. In the first draft of the episode's script (which had the working title "Equilibrium"), T'Pol asked Szon (who was later renamed Tolaris) if the statue was a representation of Surak, whereas in the final draft of the teleplay (and in the episode itself), she recognized Surak readily, not needing confirmation of the statue's identity.
In "Awakening", Surak is shown in two scenes. He at first seems relatively well. In the second scene, however, he is clearly suffering from radiation sickness until he actually dies. In the script of "Awakening", the episode's initial representation of Surak was described thus; "A Vulcan man in his 5O's, he wears a simple tunic and exudes a powerful intensity and wisdom." For his second appearance in the installment, the script described the ailing Surak with the statement, "The skin of his face is burned and peeled... his hair has partially fallen out. He's suffering from radiation sickness." Also, the ill Surak was to have demonstrated to Archer, by showing him their footprints were being scattered by wind, that "impressions fade with time," though this part of the second scene is not included in the episode's final version.
Despite not being referenced in the 2009 film Star Trek, Surak was referred to once in that film's screenplay, Sarek telling Young Spock that the reason their race followed Surak's teachings was that, long ago, the Vulcans had almost been destroyed by their own emotions. 
The Vulcan's Soul series of novels show parts of Surak's life. The final novel in the trilogy, Epiphany, states that his katra remains at Mount Seleya, ready to serve his people. Chapter "Vulcan: Six" of Spock's World by Diane Duane also details the life of Surak. In Beneath the Raptor's Wing, Surak's katra is destroyed.
According to Spock's World, Surak's father was named Stef and his mother was named T'Leia.
According to The Way of Kolinahr, Surak's father was General Solek.
In a number of Star Trek novels, particularly those written by Diane Duane, Sarek and Spock are scions of the House of Sarek (and thusly, either directly or indirectly, his descendants).