Depends on your definition of celestial body. There are superstructures of gravitationally intertwining superclusters of galaxies. For example, the one we reside in (above) is 500 million light years across.
The biggest one is the Hercules-Corona Borealis Great Wall, which is basically a structure defined by the high concentration of gamma ray bursts coming from it. It's about 10 billion light years across.
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Damn, a wall that is 10 billion light years across. I bet Donald Trump can fap to that
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That'll keep the illegal aliens out.