Microcystin-WR is primarily known for its role as a hepatotoxin produced by certain cyanobacteria during harmful algal blooms. Its main significance lies in environmental and public health monitoring. It is used as a biomarker to detect water contamination in lakes, reservoirs, and drinking water supplies, helping assess the risk of toxic blooms. Due to its high toxicity, it is also employed in research settings to study liver cell damage, oxidative stress, and the mechanisms of protein phosphatase inhibition. Additionally, it serves as a reference standard in analytical chemistry for developing detection methods such as ELISA, mass spectrometry, and HPLC to ensure water safety. Its presence triggers regulatory actions to protect aquatic ecosystems and human health.