For the mirror universe counterpart, see L'Haan (mirror).

L'Haan was a female Vulcan and senior operative of Section 31. She had shoulder-length straight black hair and was at least one hundred years older than Dietz, another Section 31 operative.

L'Haan did not have a very high opinion of Presidential Chief of Staff Koll Azernal and she considered him overrated as a strategist.

In 2379, Dietz was responsible for monitoring the Federation's situation with Tezwa and L'Haan regularly asked for updates on the situation. She ordered Dietz to prepare to destroy the entire planet of Tezwa if the Enterprise failed in its mission. Carrying out this order became unnecessary when Worf was able to obtain the Fleet Command Codes which allowed the Enterprise to take control of the entire Klingon fleet.

When it became clear that Nelino Quafina would use the Orion Syndicate to attempt to cover up the Federation's involvement in giving Tezwa their nadion-pulse cannons, L'Haan ordered Dietz to activate the Orion Sleeper. (TNG novel: A Time to Kill)

Along with her fellow operatives, L'Haan continued to monitor the actions of Azernal and Quafina, including their hiring of the merchant freighter Caedera. Once Zife's illegal actions were known to a select group of Starfleet admirals who forced him to resign, she, along with Vasily Zeitsev and Dietz, was responsible for escorting Zife to give his resignation, and then executing Zife, Azernal, and Quafina. (TNG novel: A Time to Heal)

Spoiler warning: Plot and/or ending details follow.

In 2382, L'Haan sent Sarina Douglas to Deep Space Nine to help convince Julian Bashir of the necessity to undertake a black-ops mission, sanctified by the President of the United Federation of Planets, to infiltrate the mysterious species known as the Breen, find the hidden slipstream project, and destroy it.