Praearcturus is an extinct genus of scorpion known from the Devonian[1] of what is now Britain.

It is the only genus in the family Praearcturidae and contains the single species Praearcturus gigas.

The type fossil was discovered in Rowlestone, England, and was described in 1871 by Henry Woodward.

[1][2] While type specimen is from Lower Devonian of Old Red Sandstone,[3][4] single tergite remain is known from Lower Devonian of Wyoming and fragmentary cuticles referrable to this genus is known from Famennian of Portishead.

[3][5] The species could reach a total length of nearly 1 metre (3.3 ft), making it one of the largest scorpions known.