Pujara, who on Saturday joined a select group of cricketing greats by smashing his 50th first-class century, is already the Indian player with most first class double centuries when he scored his 12th double ton in 2017 to go past Vijay Merchant.
With his 248 on Sunday, Pujara also became only the third player to record seven double centuries in Ranji Trophy. He is at joint second with Ajay Sharma two behind Paras Dogra, who played most cricket for Himachal Pradesh.
Pujara also completed 6000 runs in Ranji Trophy during the course of his marathon knock.
He and senior batsman Sheldon Jackson (161) rescued Saurashtra with a massive 394-run stand for the third wicket after they lost their two openers for only 33 runs on the board on Saturday.
Pujara resumed the second day on 162 and raised his double ton on Sunday before being eventually dismissed for 248 off 390 deliveries with help of 24 fours and a six.
In reply, Karnataka were 13 for 1 in eight overs.
Saurashtra 581 for 7 declared in 166 overs (Cheteshwar Pujara 248, Sheldon Jackson 161, Perak Mankad 86; Pravin Dubey 2/80, J Suchith 2/129) vs Karnataka 13 for 1 in 8 overs.