Donald's knock of 234 off just 136 balls included 15 sixes and 26 fours. He reached 200-run mark in 123 balls equalling the record set by former India international Shastri in 1985.
The 19-year-old came to the crease at Colwyn Bay with his side struggling at 96 for 3 in the County Championship encounter, and immediately went on the attack before reaching his maiden Championship ton with a six.
He also brought up both his 150 and 200 with sixes, before holding out to long-on after racking up 234 from only 136 deliveries. Glamorgan ended the first day on 491 for 8.