Jessie's Seviper (Japanese: ムサシのハブネーク Musashi's Habunake) was the first Pokémon caught by Jessie of Team Rocket during her travels through Hoenn, presumably as a replacement for her recently released Arbok. Its voice actress in Japanese is 佐藤智恵 Chie Satō, and its English voice actor is Michael Sinterniklaas. In the English dub, some of the noises made by Satō are retained along with Sinterniklaas's voice.
Jessie caught Seviper in A Tail with a Twist after initially being impressed with its sneaky and aggressive demeanor, despite it biting off a large portion of her beloved hair.
Seviper is Jessie's primary battling Pokémon, often seen battling alongside James's Cacnea. While shown to be fairly powerful before being caught by Jessie, after it fell into her command, it suffered the inevitable fate that all Team Rocket Pokémon face- defeat by Ash or another good character. In the episode Zig Zag Zangoose, Jessie and Seviper were determined to win a battle against Seviper's mortal enemy, a Zangoose belonging to the trainer Nicolai. She also entered it into a Contest one time, but it failed miserably when Jessie told it to use attacks Seviper can't learn. We then see her apologizing to it, meaning she does care about Seviper.
For more information on this Pokémon's species, see Seviper.