Final answer:
The Rite of Spring is the famous ballet that ushered in the romantic era.
Step-by-step explanation:
The famous ballet that is said to have ushered in the romantic era is The Rite of Spring. This ballet, composed by Igor Stravinsky and choreographed by Vaslav Nijinsky, premiered in Paris in 1913. The Rite of Spring caused a scandal at its first performance due to its groundbreaking music and unconventional choreography.