3 institutions reported holding $72.4M of MPLX LP (MPLXP) in SEC 13F filings for 2026-06-30. Largest institutional holders: GROUP ONE TRADING LLC ($40.6M), IMC-Chicago, LLC ($20.5M), SIMPLEX TRADING, LLC ($11.2M). Source: SEC Form 13F.
| Rank | Institution | Value | Shares | Change |
|---|---|---|---|---|
| 1 | GROUP ONE TRADING LLC | $40.6M | 721,100 | Added |
| 2 | IMC-Chicago, LLC | $20.5M | 364,600 | Added |
| 3 | SIMPLEX TRADING, LLC | $11.2M | 199,600 | Trimmed |
Source: SEC Form 13F filings · as of 2026-06-30