Julianna van Leeuwenhook was a Human woman. She served in the Federation Starfleet as a flag officer in the 23rd century.

Van Leeuwenhook was in charge of the Starfleet Science Center on Rifton. She was overseen by Admiral Weems, who was stationed at Starfleet Science headquarters on Vulcan.


Van Leeuwenhook assigned the USS Enterprise to investigate a pattern of ship disappearances in the nearby Cicada sector. The disappearances occurred every 27.344 star years, with another one due to happen imminently. In doing so, she had priority override authority from Starfleet Command to divert the starship from its mission to escort a convoy of freighters. Van Leeuwenhook made sure that a replacement starship would meet the convoy before they finished loading their cargo of chromium and other ores at Carson's World and would escort them to Bethulia III. (TOS - Log Two novelization: The Lorelei Signal)

Van Leeuwenhook selected the Enterprise to survey a newly-discovered class M planet before the Klingons or Romulans could get to it first. It was a choice assignment, and James T. Kirk believed that she would have had to pull some strings to get his ship assigned to that mission, but considered it a reward for successfully solving the Cicada sector mystery. The planet turned out to be Phylos II. (TOS - Log Two novelization: The Infinite Vulcan)




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