Six samba schools had 82 minutes each to parade down the 730m-long (2,400ft) arena.
Another six will compete on Monday evening before a jury crowns this year's champion in the elite Grupo Especial (Special Group) category.
The groups will be judged in 10 categories, including their percussion section, costumes and floats, and their samba song composed especially for the occasion.
Last year's champions, Unidos da Tijuca, will be the last to perform.
Some of Rio de Janeiro's top samba schools braved the rain in the city's Sambadrome on Sunday evening in an effort to win Brazil's most competitive carnival parade.