What is the biggest solid object in the universe?

Answer 1

Earth is the largest fully rock object we know of. Neutron stars are the largest solid-like object we know of, but they aren't really fully solid. Somewhere between solid and liquid.

Answer 2

The largest known solid object in the universe is the Hercules-Corona Borealis Great Wall, a massive cosmic structure made up of galaxies that stretches over 10 billion light-years across.