#ERROR! is a common message encountered in spreadsheet applications like Microsoft Excel and Google Sheets, indicating that a formula or function has failed to execute properly. This error can arise from various issues, such as incorrect cell references, unsupported operations, or data type mismatches. Users often see it when attempting to perform calculations with invalid inputs or when a referenced cell is empty. Understanding the cause of #ERROR! is essential for troubleshooting and ensuring accurate data analysis in spreadsheets.