David Gerrold (born Jerrold David Friedman; January 24, 1944) is an American science fiction screenwriter and novelist. He wrote the script for the original Star Trek episode "The Trouble with Tribbles", created the Sleestak race on the TV series Land of the Lost, and wrote the novelette The Martian Child, which won both Hugo and Nebula Awards, and was adapted into a 2007 film starring John Cusack.

Gerrold was born to a Jewish family on January 24, 1944, in Chicago, Illinois. He attended Van Nuys High School and graduated from Ulysses S. Grant High School in its first graduating class, Los Angeles Valley College, and San Fernando Valley State College (now California State University, Northridge).

Within days of seeing the Star Trek series premiere "The Man Trap" on September 8, 1966, 22-year-old Gerrold wrote a 60-page outline for a two-part episode called "Tomorrow Was Yesterday" about the Enterprise discovering a ship launched from Earth centuries earlier. Although Star Trek producer Gene L. Coon rejected the outline, he realized Gerrold was talented and expressed interest in his submitting some story premises. Bearing preliminary titles and, in some cases, preliminary character names, Gerrold submitted five premises.

Two of the submissions of which he later had little recollection involved a spaceship-destroying machine, similar to Norman Spinrad's "The Doomsday Machine", and a situation in which Kirk had to play a chess game with an advanced intelligence using his crew as chess pieces. A third premise, "Bandi", involved a small being running about the Enterprise as someone's pet, and which empathically sways the crew's feelings and emotions to comfort it, even at someone else's expense.

A fourth premise, "The Protracted Man", applied science fiction to an effect seen in West Side Story, when Maria twirls in her dancing dress and the colours separate. Gerrold's story involved a man transported from a shuttlecraft trying out a new space warp technology. The man is no longer unified, separating into three visible forms when he moves, separated by a fraction of a second. As efforts are undertaken to correct the condition and move the Enterprise to where corrective action can be taken, the protraction worsens.

Since I first wrote that damn script for Gene
And the electrical picture machine
Tribbles have chased their creator
From here to Decatur.
Nobody knows of the tribbles I've seen.

— David Gerrold

The fifth premise, "The Fuzzies", was also initially rejected by Coon, but a while later he changed his mind and called Gerrold's agent to accept it. Gerrold then expanded the story to a full television story outline entitled "A Fuzzy Thing Happened to Me...", and it eventually became "The Trouble with Tribbles". The name "Fuzzy" was changed because H. Beam Piper had written novels about a fictional alien species of the same name (see Little Fuzzy). The script went through numerous rewrites, including, at the insistence of Gerrold's agent, being re-set in a stock frontier town instead of an "expensive" space station. Gerrold later wrote a book, The Trouble with Tribbles, telling the story of producing the episode and his earlier premises.