Annual report pursuant to Section 13 and 15(d)


Cover - USD ($)
12 Months Ended
Dec. 31, 2021
Mar. 21, 2022
Jun. 30, 2021
Cover [Abstract]      
Document Type 10-K/A    
Amendment Flag true    
Amendment Description This Amendment No. 1 (the “Amendment No. 1”) to the Annual Report on Form 10-K/A of Greenwich LifeSciences, Inc. (the “Company”) for the fiscal year ended December 31, 2021, originally filed with the Securities and Exchange Commission (the “SEC”) on March 21, 2022 (the “Original Filing”) is being filed solely to include an amended Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters to include a 5% or more stockholder who was inadvertently omitted.    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2021    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2021    
Current Fiscal Year End Date --12-31    
Entity File Number 001-39555    
Entity Registrant Name GREENWICH LIFESCIENCES, INC.    
Entity Central Index Key 0001799788    
Entity Tax Identification Number 20-5473709    
Entity Incorporation, State or Country Code DE    
Entity Address, Address Line One 3992 Bluebonnet Dr.    
Entity Address, Address Line Two Building 14    
Entity Address, City or Town Stafford    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 77477    
City Area Code (832)    
Local Phone Number 819-3232    
Title of 12(b) Security Common Stock    
Trading Symbol GLSI    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company true    
Elected Not To Use the Extended Transition Period false    
Entity Shell Company false    
Entity Public Float     $ 171,492,883
Entity Common Stock, Shares Outstanding   12,951,453  
Auditor Firm ID 206    
Auditor Name MaloneBailey, LLP    
Auditor Location Houston, Texas