The two-time world champion has been away for two years and recently suffered an accident while cycling.
The collision with a car while training in Switzerland left the Spaniard with a fractured upper jaw.
But Alonso, who missed the launch of the Alpine A521, has recovered well and will be ready to go on Friday in Bahrain when the team carry out three vital days of testing.
“I feel great and in the best shape I’ve ever been before both physically and mentally,” said the 39-year-old.
While Alpine’s CEO Laurent Rossi added: “Fernando is doing very well. He had a bad accident. A bike accident is rarely something that goes easy, but he was lucky and he ended up only suffering from his jaw.
“So besides the necessary surgery and care, the rest is totally fine. Fernando is completely fit. He is totally operational.
“We are even surprised that he’s recovered so quickly. He confirmed to us almost immediately after the incident that he will be in Bahrain, which has been confirmed with his doctors
“It looks like he was right because he’s absolutely fit, and we are looking forward to seeing him next week in the car.”
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