Does the Sony FE 100-400mm f/4.5-5.6 GM OSS fit the Sony a7 III?

Yes. The Sony FE 100-400mm f/4.5-5.6 GM OSS is a Sony E lens and the Sony a7 III is a Sony E body, so it mounts natively. Both are full-frame, so 100-400mm is the true field of view — no crop factor.

Last verified 2026-06-21 · Sony E mount · Sony full-frame lens · Sony full-frame body

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What the Sony FE 100-400mm f/4.5-5.6 GM OSS gives you on the Sony a7 III

Field of view: 100-400mm (true full-frame field of view)
Maximum aperture: f/4.5-5.6 — variable across the zoom range
Type: zoom (100-400mm)
Where it lands: short telephoto on the Sony a7 III (60–104mm equivalent) — 33 of the 103 Sony E lenses reach this range here, the brightest being the Sigma 56mm f/1.4 DC DN Contemporary at f/1.4
Tagged for: Sports & action Telephoto Landscape

Anything to watch for?

No. The Sony FE 100-400mm f/4.5-5.6 GM OSS and the Sony a7 III are both Sony E full-frame, which is the fully native pairing — the lens covers the whole sensor and the marked 100-400mm is the field of view you get.

Other Sony E lenses that use the Sony a7 III's full-frame sensor

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Focal	Lens	Buy	Max aperture	Type	Coverage	Best for
100-400mm	Sigma 100-400mm f/5-6.3 DG DN OS	Amazon →	f/5-6.3	zoom	Full-frame	Sports & action Telephoto Travel
100mm	Laowa 100mm f/2.8 2x Ultra Macro APO	Amazon →	f/2.8	prime	Full-frame	Macro Portrait
90mm	Sony FE 90mm f/2.8 Macro G OSS	Amazon →	f/2.8	prime	Full-frame	Macro Portrait
90mm	Laowa 90mm f/2.8 2x Ultra Macro APO	Amazon →	f/2.8	prime	Full-frame	Macro
85mm	Sigma 85mm f/1.4 DG DN Art	Amazon →	f/1.4	prime	Full-frame	Portrait Wedding & event Low-light
85mm	Sony FE 85mm f/1.4 GM II	Amazon →	f/1.4	prime	Full-frame	Portrait Wedding & event Low-light
85mm	Sony FE 85mm f/1.8	Amazon →	f/1.8	prime	Full-frame	Portrait Low-light
85mm	Viltrox AF 85mm f/1.8 II	Amazon →	f/1.8	prime	Full-frame	Portrait Low-light

All 103 Sony E lenses fit the Sony a7 III; 76 of them use its full-frame sensor at full resolution — check any lens against this body · best lenses for the Sony a7 III

Nearby lenses on the Sony a7 III

Sigma 100-400mm f/5-6.3 DG DN OS Laowa 100mm f/2.8 2x Ultra Macro APO Laowa 65mm f/2.8 2x Ultra Macro APO Sony E 70-350mm f/4.5-6.3 G OSS Sony FE 90mm f/2.8 Macro G OSS Laowa 90mm f/2.8 2x Ultra Macro APO

FAQ

Does the Sony FE 100-400mm f/4.5-5.6 GM OSS fit the Sony a7 III?
Yes. The Sony FE 100-400mm f/4.5-5.6 GM OSS is a Sony E lens and the Sony a7 III is a Sony E body. Lens-to-body compatibility is decided by the mount, so it fits natively.

Will autofocus work?
We do not publish autofocus behaviour — FitMyLens stores only the specs that are fixed facts of the product (mount, focal length, maximum aperture, sensor coverage). Check the Sony product page for AF support on the Sony a7 III.

What focal length will I actually get?
100-400mm. The Sony a7 III is full-frame and the Sony FE 100-400mm f/4.5-5.6 GM OSS is a full-frame lens, so the marked focal length is the field of view you get.

Citing these specs? Go ahead — manufacturer data, last verified 2026-06-21. Copy a ready-made reference:

More: Sony FE 100-400mm f/4.5-5.6 GM OSS specs · Every lens on the Sony a7 III · Best lenses for the Sony a7 III · All Sony E lenses · All cameras