Joni Thrombey, played by Toni Collette, is a character in Knives Out. She is the widow of Neil Thrombey and the mother of Meg Thrombey. Joni is a famous lifestyle guru and runs a failing skincare company called Flam. She is shown as a suspect in Harlan's death.

Joni Thrombey is the owner of Flam. Flam is a skincare business that also supports a full lifestyle. Joni Thrombey, in her first meeting with the researchers, reports her company philosophy as a "balance of opposites...self-sufficiency with acceptance of human need." At first glance, it may seem like there is no problem with the company, but Detective Blanc later reveals problems with the product. She bought a moisturizer with snail jelly from Flam that caused rashes on her sensitive skin. It searches for similar consumer complaints and finds many similar complaints. Further investigation revealed Flam's financial problems. The company had gone bankrupt and Joni kept the company afloat using the money she stole from Harlan.