Cover Page - shares	6 Months Ended
	Jun. 30, 2026	Jul. 29, 2026
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2026
Document Transition Report	false
Entity File Number	000-51026
Entity Registrant Name	Monolithic Power Systems, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0466789
Entity Address, Address Line One	1555 Palm Beach Lakes Blvd.
Entity Address, City or Town	West Palm Beach
Entity Address, State or Province	FL
Entity Address, Postal Zip Code	33401
City Area Code	561
Local Phone Number	839-3999
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	MPWR
Security Exchange Name	NASDAQ
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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		49,143,000
Entity Central Index Key	0001280452
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q2
Amendment Flag	false