Introduction: Fe-sulfides are ubiquitous in chondrites and are sensitive indicators of formation and alteration conditions in the protoplanetary disk and small Solar System bodies [e.g., 1-14]. We previously constrained a minimum oxygen fugacity (fO2) needed to form pentlandite, (Fe,Ni)9S8, [6,7] and identified trends with pentlandite compositions between distinct meteorite groups [6,7]. We also identified a relationship between the at.% Fe/S ratio of pyrrhotite group sulfides and the fO2 of formation, either in the protoplanetary disk or the parent body during aqueous alteration or thermal alteration [13]. Since pentlandite formed with pyrrhotite (they are typically intergrown in these chondrite groups [1-14]), fO2 may have influenced pentlandite compositions. To increase the information gained from individual mineral systems, here we report the chemical compositions of pentlandite in chondrites that experienced a wide range of formation and parent body alteration conditions (including fO2 [13]). This will allow us to investigate a potential trend(s) with the pyrrhotite at.% Fe/S ratio, and by extension fO2. Samples and Analytical Procedures: We determined the major and minor element compositions of pentlandite in each of the following 54 chondrites: CI (Alais), a C1-ungrouped (Miller Range [MIL] 090292), C2-ungrouped (Tarda and Tagish Lake), CY (Belgica [B]-7904), CM1/2 (Allan Hills [ALH] 83100 and Kolang [two lithologies]), unheated CM2s (Aguas Zarcas [multiple lithologies], Mighei, Queen Alexandra Range [QUE] 97990, Theil Mountains [TIL] 91722, and D'Angelo Bluff [DNG] 06004), stage I heated CM2 (Asuka [A]-881458), stage II heated CM2 (Yamato [Y]-793321), CM-like (Sutter's Mill), CO3.00 (Dominion Range [DOM] 08006), CR1 (Grosvenor Mountains [GRO] 95577), CR-an (Al Rais), CR2 (Elephant Moraine [EET] 87770, EET 92048, EET 96259, Gao-Guenie (b), Graves Nunatak [GRA] 95229, LaPaz Ice Field [LAP] 02342, LAP 04720, MIL 090657, Northwest Africa [NWA] 801, Pecora Escarpment [PCA] 91082, QUE 99177, Shişr 033, and Y-793495), shock-heated CR2 (GRO 03116), CV3OxA (Allende), CV3OxB (Bali), and CV3Red (Vigarano), CK4 (ALH 85002 and Karoonda), CK5 (Larkman Nunatak [LAR] 06868), CK6 (Lewis Cliff [LEW] 87009), L3.05 (EET 90161 and QUE 97008), LL3 (Semarkona and Vicencia), LL4 (Hamlet and Soko-Banja), LL5 (Chelyabinsk and Siena), LL6 (Appley Bridge and Saint-Séverin), R3 (MET 01149), R3.6 (LAP 031275), R5 (LAP 03639), and R6 (LAP 04840 and MIL 11207) chondrites. We acquired high-resolution backscatter electron images and quantitative chemical compositions with the JEOL-8530F Hyperprobe electron microprobe analyzer (EPMA) at Arizona State University (ASU) and the Cameca SX-100 EPMA at the Uni-versity of Arizona (UA) following [13]. Some pentlandite compositions were previously reported [6,7,10,11]. Results and Discussion: Our data show that there is a relationship between the at.% Fe/S of pyrrhotite (data from [13]) and pentlandite compositions. Since the at.% Fe/S ratio of pyrrhotite is a proxy for fO2 [13], this demonstrates that there is a relationship between fO2 and pentlandite composition. Therefore, pentlandite compositions were influ-enced by the fO2 of formation. This is true whether pentlandite formed: (1) during chondrule formation in the protoplanetary disk (i.e., during chondrule cooling, as previously noted by [6,8,10,11] for CR2, CO3.00, and LL3.00 chondrites), (2) during thermal alteration on the parent asteroid under relatively reducing (i.e., LL4-6 chondrites) or oxidizing (i.e., R4-6 and CK chondrites) conditions, or (3) during oxidizing aqueous alteration (i.e., as in CI, CM1, C1-ung, and C2-ung chondrites). Therefore, in addition to the at.% Fe/S ratio of pyrrhotite, the chemical compositions of pentlandite can also be used as a proxy for the fO2 of formation. This discovery has implications for the interpreta-tion of pentlandite compositions in meteorites and in asteroid returned samples from Ryugu and Bennu. [ABSTRACT FROM AUTHOR]