"Journey to Babel" is the tenth episode of the second season of the American science fiction television series Star Trek. Written by D. C. Fontana and directed by Joseph Pevney, it was first broadcast on November 17, 1967.

In the episode, Enterprise is tasked with transporting dignitaries to a diplomatic conference.

The episode features the first appearance of Sarek (Mark Lenard) and Amanda (Jane Wyatt), the parents of Spock, and also introduces two new species, the Andorians and the Tellarites.

Enterprise, under the command of Captain Kirk, is transporting Federation ambassadors to a conference on the planet Babel to discuss the admission of the Coridan system into the Federation. The system is a prime source of dilithium crystals, but is underpopulated and unprotected, a situation some would prefer to maintain by keeping Coridan out of the Federation.

Sarek, who is a Vulcan ambassador, boards the ship with his human wife Amanda, ignoring Spock's greeting. Captain Kirk learns that Sarek is in fact Spock's father, now estranged because he had disapproved of his son's decision to join Starfleet rather than attend the Vulcan Science Academy.

During a reception for the passengers, the Tellarite ambassador, Gav, demands to know Sarek's position on Coridan. Pushed for a response, Sarek refers to the need to protect Coridan from unauthorized mining operations, with which Tellarite ships have been involved. Gav takes offense at the allegation and the confrontation briefly becomes physical before Kirk intervenes, warning all parties to keep order on his ship.

Meanwhile, Communications Officer Lt. Uhura has detected an encoded transmission beamed from Enterprise to a fast-moving vessel at the extreme edge of sensor range. Shortly afterward, Ambassador Gav is found murdered, his neck broken by what Spock describes as an ancient Vulcan method of execution called Tal-Shaya, casting suspicion on Sarek. During questioning, Sarek suffers a cardiovascular event, and is rushed to the sickbay, where Chief Medical Officer McCoy determines that he requires immediate surgery. Because there is a shortage of his rare T-negative-type blood, Spock volunteers to donate some of his own blood for the operation, using an experimental stimulant for increased blood production.

Plans for the procedure come to a halt when Thelev, a member of the Andorian delegation, stabs Captain Kirk. Kirk subdues Thelev but is seriously wounded and taken to Sickbay, while Thelev is imprisoned in the brig. In accordance with regulations, and despite Amanda's emotional plea, Spock refuses to serve as the blood donor and turn command of Enterprise over to another officer, as the situation is too critical and command regulations are silent on the matter of personal privilege.