Lieutenant Helga Katrina Sinclair is a character in Atlantis: The Lost Empire who serves as second-in-command of the expedition to find the lost continent of Atlantis. She also serves as the personal assistant to Preston Whitmore.

Miss Sinclair is skilled as a coordinator and drill instructor. She also possesses an analytical mind ideally suited for strategy, tactics or campaign planning. Her charisma, combined with her intelligence and aggressive nature, makes her an excellent trainer and enforcer.

She is the muscle behind Commander Rourke; when her commanding officer issues and order, Miss Sinclair makes it her personal business to see to it that everyone in her command follows it to the letter. She is levelheaded in a crisis (see attachment re: San Domingo, 1904) and highly skilled in many forms of small arms combat; studied Aikido in Philippines under Moreihei Ueshiba 1904-07, attaining rank of Yudansha-Yodan. Expert in disciplines of Henka Waza, Tanto Dori and Tachi Dori.

Born in Frankfurt, Germany as the daughter of career officer U.S. Army Major Alexander Sinclair. Extensive travel at an early age, as well as exposure to a variety of cultures and customs (Frankfurt 1884-87, Mannheim 1887-89, Stuttgart 1889-92, Torii Station 1892, Vicenza 1892-93, Camp Zama 1893-94, Yongsan 1894-97, Aberdeen Proving Ground, 1897-1901). Miss Sinclair exhibited exceptional athletic skill at the age of four, and was encouraged by her mother to pursue dance.

“And relax. He doesn’t bite… often.”