By Brazil Stock Guide – Cosan SA (CSAN3) endured one of its steepest stock declines in recent years, according to data from Elos Ayta. On Sept. 22, 2025, the company’s shares tumbled 18.13%, erasing about $460 million in market value. The loss in a single day was equivalent to the entire market capitalization of Companhia Brasileira de Alumínio (CBA3), currently worth $460 million. Cosan closed the session valued at approximately $2.1 billion.
Intraday, losses were even deeper, with shares down as much as 24.93%, a temporary hit of around $640 million.
From peak to free fall
The downturn underscores Cosan’s four-year slide since its peak on July 22, 2021, when the company reached a market capitalization of $9.2 billion. Since then, its trajectory has been marked by successive declines, bottoming out at $1.76 billion on Aug. 21, 2025.
From that record high, Cosan has lost nearly $7.5 billion in value — almost the same as the current market capitalization of Localiza (RENT3), at about $7.6 billion. Considering only the period between the July 2021 peak and Sept. 22, 2025, the accumulated decline totals $7.2 billion, a figure larger than Copel’s (CPLE6) current valuation of $6.9 billion.
Mounting pressure
Charts tracking Cosan’s performance reveal a persistent downward spiral since 2021. Brief recoveries have consistently been followed by fresh selloffs, leaving the company under mounting pressure and investors wary of its prospects for recovery.
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