Cover - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2022	Feb. 24, 2023	Jun. 30, 2022
Cover [Abstract]
Entity Central Index Key	0001806952
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Amendment Flag	false
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2022
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-40502
Entity Registrant Name	Lyell Immunopharma, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-1300510
Entity Address, Address Line One	201 Haskins Way
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	695-0677
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	LYEL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 1.1
Entity Common Stock, Shares Outstanding		249,609,247
Documents Incorporated by Reference	Portions of the registrant’s Proxy Statement for the 2023 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10-K to the extent stated herein. Such proxy statement will be filed with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2022.