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While star cameras and wide angle cameras in space are built from glass lenses, large aperture optical systems generally use reflective optics. For some large ones see answers to What's the largest aperture telescope sent beyond the Earth-Moon system?.

Discussion in comments below the question Why does LRO's laser altimeter telescopes use lenses instead of mirrors? where what looks like a pretty big lens has got me wondering.

Question: What's the largest optical lens put in space?

Optical could include infrared, visible and ultraviolet, but not microwaves. It could be an objective lens or a part of a larger optical assembly of mixed elements, or it could still be in its shipping crate.

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    $\begingroup$ Are you asking for the biggest telescope using only optical lenses or can the "largest optical lens put in space" also be a sub-component from a telescope which uses mirrors as it "main" optical components? $\endgroup$
    – GittingGud
    Jun 3, 2019 at 5:33
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    $\begingroup$ @GittingGud either way would be fine. "largest optical lens put in space" can be taken literally. It could be part of a larger optical assembly of mixed elements, or in a birthday cake if that's what it takes. I've adjusted the wording, Thanks! $\endgroup$
    – uhoh
    Jun 3, 2019 at 5:43
  • $\begingroup$ follow-up question: What's the largest optical telescope mirror every put in space? $\endgroup$
    – uhoh
    Jun 3, 2019 at 16:02
  • $\begingroup$ Probably classified. The main use of large-scale optics in space is spy satellites. $\endgroup$
    – Mark
    Jun 7, 2019 at 1:28

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There doesn't seem to be a lot of discussion of actual optical lenses because they are mainly used on spy satellites. This is because the large, compound telephoto camera lenses can produce diffraction-limited images over a wider field of view than their long focal length mirror based telescope cousins used to take pictures of the stars.

For instance this Soviet spy satellite lens from a Yantar spy satellite seems to be quite large

The lens itself comes in at 348.3 pounds, is 4-foot-2-inches long, and has a diameter of 27.5 inches at its widest.

Soviet satellite spy camera lens

Such data seems to be rare, however. This article about Gaofen 4 (Chinese satellite) has this note

This scientific article by Beijing Institute of Space Mechanics and Electricity's Zhang Yue, Wang Chao, Su Yuan and Jiao Jianchao, describes temperature control on a 20+ meter diameter mirror made of optical membrane foil (a smaller satellite can unfold the optical membrane foil to create a larger lens to enable higher resolution).

So... is that a giant mirror or a giant lens? The Chinese government won't really say...

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