Handel began the music in December 1736; the premiere took place at Covent Garden Theatre in London on 18 May 1737 — but was unsuccessful, with just three further performances.
An enormous success, Rinaldo created a craze in London for Italian opera seria, a form focused overwhelmingly on solo arias for the star virtuoso singers.
[2] None of Handel's three new operas in the 1736–37 season repeated the success of his earlier works, and he suffered a breakdown in his health, as reported by his friend Lord Shaftesbury: "Great fatigue and disappointment, affected him so much, that he was this Spring struck with the Palsy, which took entirely away, the use of 4 fingers of his right hand; and totally disabled him from Playing: And when the heats of the Summer 1737 came on, the Disorder seemed at times to affect his Understanding.
The Queen, Berenice, has for some time been in love with a prince of Macedonia, Demetrio, but has been advised that for the good of her country she must form an alliance with Rome through marriage, and she has reluctantly consented to set aside personal feeling for duty.
Fabio, the Roman ambassador, presents the Queen with the man chosen by them to be her husband, Prince Alessandro of Rome.
Alessandro falls madly in love with Berenice at first sight, but she is not as impressed with him and resents having a husband forced on her in this way.
Fabio tells Alessandro that if Berenice refuses to marry him, he must wed her sister Princess Selene, instead.
Moreover, they are plotting to call Mithridates to their aid to overthrow Berenice and put Selene on the throne in her place.