Cover and table of contents

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

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FORM 10-Q

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For the quarterly period ended June 30, 2026

OR

Commission file number: 000-51026

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Monolithic Power Systems, Inc.

(Exact name of registrant

as specified in its charter)

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1555 Palm Beach Lakes Blvd.,

West Palm Beach, Florida 33401

(Address of principal executive offices)(Zip Code)(1)

(561) 839-3999

(Registrant’s telephone number, including area code)

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Securities registered pursuant to Section 12(b) of the Act:

(1)We have operations in multiple locations in the U.S., Europe and Asia and have not identified a single location as the Company’s headquarters. We are including this address to comply with the Securities and Exchange Commission’s requirements.

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes x No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No x

There were 49,143,000 shares of the registrant’s common stock issued and outstanding as of July 29, 2026.

MONOLITHIC POWER SYSTEMS, INC.

Form 10-Q

For the Quarter Ended June 30, 2026

TABLE OF CONTENTS

PART I. FINANCIAL INFORMATION