Katrina Cornwell
Vice Admiral Katrina "Kat" Cornwell was a Human female Starfleet flag officer who lived during the mid-23rd century. At one time she had been a therapist, and she had experience treating PTSD. ()

History 

Cornwell was an old acquaintance of Gabriel Lorca, with the two of them being on a first-name basis. ()

At some point before the Federation-Klingon War, Cornwell visited Section 31 Headquarters. She did not visit it during the war. ()

Federation-Klingon War

Ordering Lorca to Corvan II
In November of 2256, she informed Lorca – who had by then been replaced by  from a parallel universe and made captain of the  – about a concurrent Klingon attack on Corvan II and ordered him to protect that planetoid. ()

Strategy meeting

In December of 2256, she attended a strategy briefing with Lorca, Terral, and three other admirals. She ordered Lorca to restrict the use of the spore drive since the Klingons might have learned of it and might target the Discovery. ()

Visiting Discovery
A week later, she visited the Discovery after Lorca launched an unauthorized rescue mission for Ambassador Sarek, whose ship had been disabled on the way to a diplomatic mission by an explosion that had deliberately been caused by an aide who had turned out to be a logic extremist. Cornwell and Lorca attempted to rekindle their romantic relationship. However, Cornwell made the decision to declare Lorca unfit for command after she tenderly awoke him the morning after, and he responded with a phaser in one hand and his other at her throat (due to lingering trauma relating to Lorca having recently served time in a Klingon prison; she was quite upset he kept a phaser under his pillow).

Capture on Cancri IV

However, Sarek was too injured to attend his diplomatic mission to Cancri IV, a meeting with a supposed dissenting Klingon faction which could end the war, so Cornwell took Sarek's place, planning to recommend Lorca be stripped of command afterward. The mission turned out to be a trap orchestrated by Klingon General , and Cornwell was captured by Dennas and Ujilli. ()

Prisoner of war
Sometime later, Cornwell was kept prisoner by Kol aboard the Sarcophagus. Despite weeks of torture, she refused to give up any information. L'Rell offered her services to Kol as an interrogator in exchange for a cloaking device, but this was a ruse in order to get close to Cornwell. The imprisoned admiral met L'Rell when the latter arrived in her cell. At her insistence, Cornwell screamed, which she used to distract a guard away from the area. The admiral also learned that L'Rell wanted to defect to the Federation in exchange for helping her escape, the Klingon having grown disillusioned with how easy her people fell in line with Kol.

Attempted escape with L'Rell

However, during the escape, L'Rell and Cornwell were confronted by Kol. Realizing they were unlikely to escape, Cornwell grabbed L'Rell's blade and attacked her, in order to maintain the illusion in front of Kol's men. Afterward, L'Rell hid the unconscious Cornwell in a side room – a room which, to L'Rell's horror, was filled with corpses. ()

Rescue
When  and Michael Burnham infiltrated the Sarcophagus to place sensors on the ship to allow Discovery to detect the Klingon ship while it was cloaked, the pair picked up Cornwell's life signs and found her in the side room where she had been placed earlier.  Discovering L'Rell present in the same room, Tyler began experiencing intense flashbacks, and was unable to continue the mission. Burnham went on to complete the placement of the sensor on the bridge, while Cornwell tried to bring Tyler back to reality.

After Burnham successfully completed the placement of the sensors, Cornwell was beamed back to the Discovery along with Tyler, Burnham, and L'Rell. Cornwell was sent by emergency medical shuttle to Starbase 88 where she underwent surgery. She was expected to make a total recovery. ()

Discoverys return

Following the Discoverys return from the mirror universe without Captain Lorca, Cornwell was visibly angered upon hearing of his betrayal, and upset at the presumed death of his prime universe counterpart. She assumed temporary command of the Discovery and took it to Starbase 1, only to discover that the starbase had been overrun and occupied by Klingon forces. When the mirror universe version of  proposed that the Federation strike the Klingon homeworld of Qo'noS directly, by detonating a bomb inside its mantle and rendering it uninhabitable, Cornwell supported the plan, even going so far as to help Georgiou masquerade as her deceased counterpart.

However, upon discovering Georgiou's plan, the Discoverys crew objected to the genocide they were about to be complicit in and threatened mutiny. When Specialist Burnham pointed out that Cornwell was making the same mistake she herself had made just before the Battle of the Binary Stars – forgoing Starfleet principles for the sake of survival – Cornwell abandoned the plan. Instead, she authorized Burnham to give L'Rell the bomb's detonator so that L'Rell could use it as leverage to take charge of the Klingon Empire and end hostilities. Cornwell later honored the crew of the Discovery for their actions during the war. ()

Post-war

The red bursts
Some weeks following the appearance of the red bursts across the galaxy, Cornwell learned that Discovery and Section 31, in spite of having the same objective (to find Spock and to find out what links him to the Red Angel), were starting to step on each other's toes at the expense of their mission. Cornwell arranged a meeting with Pike, captain of the Discovery, and Leland, the Section 31 agent handling the Spock case, to force them to find common ground concerning the search for Spock. ()

She later arrived aboard Discovery via shuttlecraft to interrogate Spock herself. The questioning revealed that Spock was telling the truth when he denied being a murderer, or at least that he was convinced that he was telling the truth. She also revealed to Pike that Admiral Patar was a logic extremist. She remained on board the Discovery for a mission to Section 31 Headquarters. It was there that she learned that Patar, and most of Section 31's leadership, had been killed by Control. ()

She was still on board during a joint mission between Discovery and NCIA-93 to Essof IV to capture the Red Angel. ()

Death
Cornwell died in the line of duty in 2258, during a pitched battle against Control. After a torpedo, fired from Control's fleet, lodged itself in the hull of the , Cornwell attempted to disable the torpedo. However, the attempt was unsuccessful, and Cornwell was forced to seal the blast doors from the inside. The torpedo detonated, killing Cornwell and causing considerable damage to the Enterprise, but Cornwell's sacrifice prevented the device from destroying the ship outright. ()

Key dates 
 Between 2256 and 2257: Orders the USS Enterprise to sit out the Federation-Klingon war
 2257:
 Temporarily assumes command of the  after its return from the mirror universe. Later gives commands to .
 2258:
 Temporarily assumes command of the  before transferring command back to Christopher Pike 
 Dies during the Battle near Xahea, sacrificing herself in order to prevent the Enterprise from being completely destroyed by an undetonated photon torpedo.

Memorable quotes 
"I can't leave Starfleet's most powerful weapon in the hands of a broken man."
"Don't take my ship away from me. She's all I got. Please, I'm begging you."
 - Katrina Cornwell and Gabriel Lorca, on Lorca's ability to command the USS Discovery ()

"The Discoverys been through– an inconceivable ordeal."
"Then where the hell is her commanding officer?"
"Captain – is dead."
- Sarek and Katrina Cornwell ()

"Bastard! The Lorca I came up with was measured, he was reasoned. I couldn't have imagined..."
"That Lorca was an impostor from an alternate universe was not the most obvious conclusion. We were all deceived."
- Katrina Cornwell and Sarek, on Lorca's true colors ()

"You sat out the war because if we'd lost to the Klingons, we wanted the best of Starfleet to survive. And as this conversation makes clear, that was you… and all you represent."
"Thank you."
"You're welcome. Now, will you get off my ass so we can get back to work?"
 - Cornwell and Pike, on why the Enterprise was kept out of the war ()

"Admiral, we have a solution."
"I'm cringing already."
 - Leland and Cornwell on capturing the Red Angel ()

"And Chris? Whatever your path may be, you can handle it."
- Katrina Cornwells last words to Christopher Pike ()

Appendices

Appearances

Background information 
Cornwell was portrayed by actress Jayne Brook.

The first name "Katrina" was initially only mentioned in the Netflix German voice dubbing list for , but was first spoken in the following episode, .

In the  of , shown after "Choose Your Pain", showrunners Gretchen Berg and Aaron Harberts mentioned that Cornwell is a psychiatrist by training, who is not only old friends with Lorca, but is assessing him as she supervises him, and is worried about him.

When asked how Cornwell would handle Saru's "break from reality" in , Jayne Brook commented that the admiral would try to talk Saru down slowly rather than threaten to remove him from serving on his ship. Brook went on to say, "I think that she would give him time. I think she's a measured person who gives people the space, or wants to give them the space, to heal, and to observe herself. I think she would observe him a
nd give him time." ()

Dialog in  and  further implies that Cornwell had the title of doctor.

Cornwell was a vice admiral, as her badge was consistent with this rank. She was referred to onscreen as "admiral", as an admiral of any rank was, as an honorific.

External links 
 
 
 

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ru:Катрина Корнуэлл
Humans
Starfleet flag officers
Starfleet personnel (23rd century)