The 29 year-old's 15-month ban for testing positive for meldonium ends on April 26 and the event in Germany starts on the 24th.
However, three-time winner Sharapova, whose main sponsor is Porsche, has been handed a wild card to the tournament and will play her first match without a ranking on the day the ban finishes.
In a statement WTA said: "Five-time Grand Slam champion Maria Sharapova becomes eligible to play WTA tournaments on Wednesday, April 26, following a 15-month suspension.
"As both a former Grand Slam champion and WTA Finals winner, Sharapova may request and receive an unlimited number of wildcard nominations, including the Porsche Tennis Grand Prix (in Stuttgart), where she will make her return.
"In compliance with WTA and the Tennis Anti-Doping Programme rules, Sharapova can participate in a tournament in the week that her suspension ends, providing that the first match that she is scheduled to contest takes place on or after the day on which she is eligible to return to competition."
WTA players, including Caroline Wozniacki, have criticised the organisers for inviting Sharapova to the tournament and allowing her to start the tournament later at other players' expense.
"I think it's very questionable, allowing - no matter who it is - a player that is still banned to play a tournament that week," said Wozniacki. "I think it's disrespectful to the other players and the WTA.
"But, you know, it is what it is. Obviously rules are twisted and turned in favour of who wants to do what."
Sharapova has already picked up wild cards for tennis tournaments in Stuttgart, Madrid and Rome whilst serving her provisional suspension.