Brazil’s original republican flag, adopted in 1889, had 21 stars.
The republic adopted the flag on 19 November 1889, four days after the monarchy was overthrown. Its green field and yellow rhombus retained visual links to the imperial flag, while a blue celestial globe, white stars, and the motto “Ordem e Progresso” replaced the imperial coat of arms.
The 21 stars represented Brazil’s federal units at the time: the 20 states plus the Federal District. The number later increased as Brazil’s political map changed. One star was added in 1960, another in 1968, and four more in 1992, producing the 27-star design used today.
A frequent mistake is to answer 27 because that is the number on the modern flag. The question asks specifically about the original republican version from 1889, so 21—not the current total—is the canonical answer.