Document and Entity Information - shares	9 Months Ended
	Jun. 30, 2020	Jul. 30, 2020
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-33288
Entity Registrant Name	HAYNES INTERNATIONAL, INC.
Entity Central Index Key	0000858655
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	06-1185400
Entity Address, Address Line One	1020 West Park Avenue
Entity Address, City or Town	Kokomo
Entity Address, State or Province	IN
Entity Address, Postal Zip Code	46904-9013
City Area Code	765
Local Phone Number	456-6000
Title of 12(b) Security	Common Stock, par value $.001 per share
Trading Symbol	HAYN
Security Exchange Name	NASDAQ
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		12,556,921
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3