Cover Page - shares	9 Months Ended
	Sep. 30, 2020	Oct. 30, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-35676
Entity Registrant Name	PROTHENA CORPORATION PUBLIC LIMITED COMPANY
Entity Incorporation, State or Country Code	L2
Entity Tax Identification Number	98-1111119
Entity Address, Address Line One	77 Sir John Rogerson’s Quay, Block C
Entity Address, Address Line Two	Grand Canal Docklands
Entity Address, City or Town	Dublin 2,
Entity Address, Postal Zip Code	D02 T804,
Entity Address, Country	IE
Country Region	353
City Area Code	1
Local Phone Number	236-2500
Title of 12(b) Security	Ordinary Shares, par value $0.01 per share
Trading Symbol	PRTA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Ordinary Shares Outstanding		39,921,413
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001559053
Current Fiscal Year End Date	--12-31