NCIS stands for Naval Criminal Investigative Service, which is what this wiki is all about.
 Leroy Jethro Gibbs
Leroy Jethro Gibbs is a main character of the show, and has been in all the seasons so far. He is a former marine sniper and now leads the Major Case Response Team. He has had 3 ex wives. His close friends include Doctor Donald Mallard and Abigail Sciuto
 Anthony DiNozzo
Anthony DiNozzo is the Senior Agent. He is an ex Baltimore cop. He loves movies and quotes them alot. He also finds a way to relate a movie to a case. He loves the show Magnum P.I. and has a bad record with women. He has been in all the seasons so far and a main character.
 Ziva David
Ziva David was a Mossad liason officer until Season 7 in which she became a full NCIS agent and an US citizen. Her father Eli David is the Director of Mossad. She first appeared in Season 3 and has been in teh series since then.
 Timothy McGee
Timothy McGee joined the show permanently in Season 2 but appeared a few tiems in Season 1. Until Season 7 he was called 'probie' by Tony. Graduated from MIT. Had a relationship with Abigail Sciuto. writes a book series Deep Six under hte alias 'Thom. E. Gemcity based on the cases he does.
 Abigail Sciuto
Abigail Sciuto is a close friend of Gibb's. She is the forensic scientist and is also a goth. Described in Season 7 by Anthony DiNozzo as 'the happiest goth you will ever meet'. Had a relationship with Timothy McGee. Has been in the show since Season 1
 Donald Mallard
Donald Mallard is the Medical Examiner. He is called 'Ducky' by his friends. His mother died in Season 7. He has a habit of telling long stories. He talks to the bodies he is doing the autopsy on. Has been in the series since Season 1
 Jimmy Palmer
Assistant to Donald Mallard. Has tinnitus and is clastrophobic. Wants to be a medical examiner and a field agent. Called 'the autopsy gremlin' by Anthony DiNozzo. Replaced Gerald Jackson as the assistant after Ari Haswari shot Gerald in the arm. Starts to take after Ducky and he seems frightened of Gibbs. First arrived in Season 2
 Leon Vance
 Jenny Shepard
 Caitlyn Todd
 Gerald Jackson
 Non NCIS characters
 Tobius Fornell
CIA agent married Gibbs second wife but got a divorce. Friends with Gibbs. They have conversations in the elevator at NCIS
 Jeanne Benoit
Fell in love with Tony when he was working undercover to get to her father.
 Mike Franks
Gibbs former boss when NCIS was still caled NIS. He had a son who was killed in Season 4. Was killed by the Port to Port killer.
 Ari Haswari
Ari Haswari shot Gerald Jackson in the arm while holding Donald Mallard and Caitlyn Todd hostage in Autopsy. Killed Kate at the end of Season 2 Was killed by his half-sister Ziva David in Gibbs basement.
 Season 1
The plot of Season 1 is showing the relationships of the characters. Caitlyn Todd joins the team in the first episode. It introduces the antagoniser for the first two seasons Ari Haswari and introduces Jimmy Palmer and Timothy McGee who appeard frequently then on.
 Season 2
 Season 3
Season 3 starts off with a two part first episode in which Gibbs hunts down Ari Haswari. It introduces Ziva David as the new female character and Jenny Shepard as teh new Director and Gibbs love intrest.