Updated: March 16, 2022

Lost in Space is a science fiction TV series created and produced by Irwin Allen, filmed by 20th Century Fox Television, and broadcast on CBS. The show ran for three seasons, with 83 episodes airing between September 15, 1965, and March 6, 1968 (the unaired pilot "No Place To Hide" and the 1998 reunion "Lost In Space Forever" bring the total number of episodes to 85). Their first TV season was filmed in black and white, but the rest were filmed in color. In 1998, a Lost in Space movie, based on the TV series, was released.

Though the TV series concept centered on the Robinson family, many storylines focused primarily on Dr. Zachary Smith (Jonathan Harris), originally an utterly evil would-be killer who became a sympathetic anti-hero by the end of the first season, providing comic relief to the TV show (and causing most of the episodic conflict).

The first appearance of a space-faring Robinson family (unrelated to the series' Robinsons) was in a comic book published by Gold Key Comics, The Space Family Robinson, December 1962. The TV series is an adaptation of the novel The Swiss Family Robinson. The astronaut family of Dr. John Robinson, accompanied by an Air Force pilot and a robot, set out from an overpopulated Earth in the spaceship Jupiter-2 to visit a planet circling the star Alpha Centauri with hopes of colonizing it. Their mission in 1997 (the official launch date of the Jupiter-2 was October 16, 1997) is immediately sabotaged by Dr. Zachary Smith, who slips aboard their spaceship and reprograms the robot to destroy the ship and crew. Smith is trapped aboard, saving himself by prematurely reviving the crew from suspended animation. They save the ship, but consequent damage leaves them lost in space. Eventually they crash on an alien world, later identified as Priplanis, where they must survive a host of adventures. Smith (whom Allen originally intended to kill off) remains through the series as a source of comedic cowardice and villainy, exploiting the forgiving (or forgetful) nature of the Robinsons.

At the start of the second season, the repaired Jupiter-2 launches again, but after two episodes the Robinsons crash on another planet and spend the season there. This replicated the feel of the first season, although by this time the focus of the series was more on humor than straight action / adventure.

In the third season, the Robinson Family wasn't restricted to one world. The now mobile Jupiter-2 would travel to other worlds in an attempt to return to Earth or to settle on their originally desired planet in the Alpha Centauri system. The Space Pod was added as a means of transportation between the ship and planets. This season had a dramatically different opening credits sequence.

Following the format of Allen's first TV series, Voyage to the Bottom of the Sea, fantasy-oriented adventure stories were emphasized. The show delivered a visual assault of special effects, explosions, monstrous aliens, spaceships, and exotic sets and costumes drenched in the bright, primary colors that were typical of early color television.

On October 16, 1997 (thirty years into the future in 1967), the United States is about to launch of one of history's great adventures: man's colonization of deep space. The Jupiter-2 (called Gemini 12 in the pilot episode), a futuristic saucer-shaped spaceship, stands on its launch pad undergoing final preparations. Its mission is to take a single family on a five-and-a-half-year journey (stated as 98 years in the pilot episode) to a planet of the nearby star Alpha Centauri (the pilot episode refers to the planet itself as Alpha Centauri), which space probes reveal possesses ideal conditions for human life. The Robinson family was selected from among two million volunteers for this mission. The family includes Professor John Robinson (Guy Williams), his wife, Maureen (June Lockhart), their children, Judy (Marta Kristen), Penny (Angela Cartwright), and Will (Billy Mumy). They will be accompanied by their pilot, US Space Corps Major Donald West (Mark Goddard), who is trained to fly the ship in the unlikely event that its sophisticated automatic guidance system malfunctions.

Other nations are racing to colonize space and they would stop at nothing, even sabotage, to thwart the US effort. Dr. Zachary Smith (Jonathan Harris), a medical doctor and environmental control expert, is actually a foreign secret agent. He reprograms the Jupiter-2's B-9 environmental control robot (voiced by Dick Tufeld) to destroy critical systems on the spaceship eight hours after launch. Smith is trapped aboard at launch and his extra weight throws the Jupiter-2 off course, causing it to encounter a meteor storm. This plus the robot's rampage causes the ship to become lost.

The Robinsons are often placed in danger by Smith, whose self-centered actions and laziness endanger the family. In the second and third seasons, Smith's role assumes a less evil overtone – although he continues to display many character defects. In "The Time Merchant", Smith travels back in time to the day of the Jupiter-2 launch, with hope of changing his fate. He learns that without his weight altering the ship's course, it would be destroyed by an uncharted asteroid. In an act of redemption, Smith elects to re-board the ship, thus saving the Robinsons' lives.