|“||Oh, one by one. The last species falls neatly into place! Ha ha ha!||„|
|~ Martin Brisby|
|“||Of course you're sorry, everyone's always sorry, AFTER IT'S TOO LATE!!!!||„|
|~ Martin to Timothy.|
Martin Brisby is a supporting character in Don Bluth's 1st animated feature The Secret of NIMH, and the hidden main antagonist in its 1998 sequel The Secret of NIMH 2: Timmy to the Rescue. He is the second-oldest child of the Brisby Family who becomes a twisted psychopathic villain after being experimented on by Dr. Valentine.
Martin is Timmy's brother and son of Mrs. Brisby. He was captured by NIMH. He became insane when the doctors brainwashed him. After being made insane, Martin took over the lab and brainwashed Dr. Valentine with a device similar to the one Valentine used on him and made him think he was a dog. Martin plans to use an army of lab rats riding a flock of ravens to take over Thorn Valley.
He asks Timmy to join him, but he refuses and is locked in a cage as Martin drags Jenny away to try to make her his queen. Timmy escapes with the help of Cecil and they go to free Jenny. Together, they knock out Martin and Timmy tricks Martin's army of ravens and rats to fly in the wrong direction.
Timmy and Jenny then leave to find the others, only to find once everyone is free that NIMH is on fire. The survivors (Timmy, Jenny, and her parents, as well as Justin and Brutus) flee. Timmy goes back to save Martin. Before he leaves, Jenny tells him she loves him and he tells her the same.
After being attacked by the cats Muriel and Floyd once again, Timmy sends them down an elevator shaft and finally finds Martin, actually, Martin finds him. Timmy and Martin are able to escape through the lab's skylight, with some help from Jeremy. Jeremy takes the survivors to safety. The mice return to Thorn Valley, and Martin returns to normal.
- Despite the fact that he was brainwashed by Dr. Joseph Valentine, Martin is the main antagonist of the film because he had bigger plans than anyone else.
- In his villainous ego in the sequel, Martin bears a somewhat resemblance to Warren T. Rat (without his disguise) from An American Tail.