OBJECTIVES: While past work studies public concern about "Long COVID," fewer have asked what the public knows and/or purports to know about Long COVID. This is an important oversight, as low knowledge and/or "meta-ignorance" (Dunning Kruger Effect
DKE) concerning Long COVID might undermine public willingness to take action to protect themselves and others from endemic COVID-19. STUDY DESIGN: In a nationally representative survey of US adults, we measure the correspondence between Americans' objective and perceived Long COVID knowledge. METHODS: We estimate a series of multivariate regression models that assess (a) the socio-demographic correlates and (b) public health consequences of Long COVID meta-ignorance. RESULTS: We detect prevalent meta-ignorance about Long COVID. Greater than one fifth of Americans express high confidence in their perceived Long COVID knowledge, despite exhibiting lower than average objective knowledge. The expression of DKE is associated with a series of deleterious public health and health policy outcomes, including: opposition to workplace COVID-19 vaccine mandates, annual COVID-19 vaccine hesitancy, and an increased likelihood of being sick with Long COVID. CONCLUSION: Our work provides novel insights into the promises and potential limitations of health communication efforts to provide the public with basic facts about the causes and consequences of Long COVID.