UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F COVER PAGE
OMB APPROVAL
OMB Number:3235-0006
Expires:July 31, 2015
Estimated average burden
hours per response:23.8
Report for the Calendar Year or Quarter Ended:
09-30-2025
Check here if Amendment: ☐ Amendment Number:
This Amendment (Check only one.):☐ is a restatement.
☐ adds new holdings entries.

Institutional Investment Manager Filing this Report:

Name:
Mountaineer Partners Management, LLC
Address:
950 3rd Avenue
28TH FLOOR
New York, NY 10022
Form 13F File Number:
028-19269

The institutional investment manager filing this report and the person by whom it is signed hereby represent that the person signing the report is authorized to submit it, that all information contained herein is true, correct and complete, and that it is understood that all required items, statements, schedules, lists, and tables, are considered integral parts of this form.


Person Signing this Report on Behalf of Reporting Manager:
Name:
Mark Lee
Title:
Managing Member
Phone:
646-459-7061


Signature, Place, and Date of Signing:

/s/Mark Lee
                         [Signature]
New York, NEW YORK
                 [City, State]
11-14-2025
                           [Date]
                          

Report Type (Check only one.):

☒ 13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager are reported in this report.) 

☐ 13F NOTICE. (Check here if no holdings reported are in this report, and all holdings are reported by other reporting manager(s).) 

☐ 13F COMBINATION REPORT. (Check here if a portion of the holdings for this reporting manager are reported in this report and a portion are reported by other reporting manager(s).)


Form 13F Summary Page

Report Summary:

Number of Other Included Managers:
0
Form 13F Information table Entry Total:
36
Form 13F Information table Value Total:
171947303
          (thousands)

List of Other Included Managers:

Provide a numbered list of the name(s) and Form 13F file number(s) of all institutional investment managers with respect to which this report is filed, other than the manager filing this report.
[If there are no entries in this list, state "NONE" and omit the column headings and list entries.]

  
NONE


UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F INFORMATION TABLE
OMB APPROVAL
OMB Number:3235-0006
Expires:July 31, 2015
Estimated average burden
hours per response:23.8
COLUMN 1COLUMN 2COLUMN 3COLUMN 4COLUMN 5COLUMN 6COLUMN 7COLUMN 8
VALUESHRS ORSH/PUT/INVESTMENTOTHERVOTING AUTHORITY
NAME OF ISSUERTITLE OF CLASSCUSIP(x$1000)PRN AMTPRNCALLDISCRETIONMANAGERSOLESHAREDNONE
ALCOA CORPCOM0138721067,738,853235,295SHSOLE235,295 0 0
ALCOA CORPCOM0138721062,017,70361,347SHSOLE 0 0 61,347
ARDAGH METAL PACKAGING S ASHSL022351064,674,9791,171,674SHSOLE1,171,674 0 0
ARDAGH METAL PACKAGING S ASHSL022351061,463,572366,810SHSOLE 0 0 366,810
ATI INCCOM01741R1029,596,412117,979SHSOLE117,979 0 0
ATI INCCOM01741R1022,118,17526,041SHSOLE 0 0 26,041
BUILDERS FIRSTSOURCE INCCOM12008R1075,728,82047,248SHSOLE47,248 0 0
BUILDERS FIRSTSOURCE INCCOM12008R1071,638,20913,511SHSOLE 0 0 13,511
CARPENTER TECHNOLOGY CORPCOM1442851032,100,3498,554SHSOLE 0 0 8,554
CARPENTER TECHNOLOGY CORPCOM1442851037,929,71432,295SHSOLE32,295 0 0
CENTURY ALUM COCOM1564311082,082,79870,940SHSOLE 0 0 70,940
CENTURY ALUM COCOM15643110817,325,424590,103SHSOLE590,103 0 0
CONSTELLIUM SECL A SHSF2110710110,403,620699,168SHSOLE699,168 0 0
CONSTELLIUM SECL A SHSF211071012,002,967134,608SHSOLE 0 0 134,608
D R HORTON INCCOM23331A1093,647,16421,521SHSOLE21,521 0 0
D R HORTON INCCOM23331A1091,076,9826,355SHSOLE 0 0 6,355
ENTEGRIS INCCOM29362U1042,010,45021,744SHSOLE 0 0 21,744
ENTEGRIS INCCOM29362U1049,383,765101,490SHSOLE101,490 0 0
EVERUS CONSTR GROUPCOM3004261032,129,85924,838SHSOLE 0 0 24,838
EVERUS CONSTR GROUPCOM30042610312,434,265145,006SHSOLE145,006 0 0
FREEPORT-MCMORAN INCCL B35671D8579,411,506239,967SHSOLE239,967 0 0
FREEPORT-MCMORAN INCCL B35671D8572,121,09654,082SHSOLE 0 0 54,082
HUDBAY MINERALS INCCOM44362810212,426,925819,718SHSOLE819,718 0 0
HUDBAY MINERALS INCCOM4436281022,057,227135,701SHSOLE 0 0 135,701
KIRBY CORPCOM4972661064,210,88750,460SHSOLE50,460 0 0
KIRBY CORPCOM4972661061,249,33014,971SHSOLE 0 0 14,971
NEXGEN ENERGY LTDCOM65340P1061,158,765129,471SHSOLE 0 0 129,471
NEXGEN ENERGY LTDCOM65340P1063,893,572435,036SHSOLE435,036 0 0
SAN JUAN BASIN RTY TRUNIT BEN INT7982411053,325,787550,627SHSOLE550,627 0 0
SAN JUAN BASIN RTY TRUNIT BEN INT7982411051,017,299168,427SHSOLE 0 0 168,427
STANDARDAERO INCCOM85423L1036,114,215224,046SHSOLE224,046 0 0
STANDARDAERO INCCOM85423L1031,819,80666,684SHSOLE 0 0 66,684
URANIUM ENERGY CORPCOM9168961033,361,200251,964SHSOLE251,964 0 0
URANIUM ENERGY CORPCOM916896103920,30068,988SHSOLE 0 0 68,988
VISHAY INTERTECHNOLOGY INCCOM9282981081,957,926127,969SHSOLE 0 0 127,969
VISHAY INTERTECHNOLOGY INCCOM9282981089,397,382614,208SHSOLE614,208 0 0