Spanish police said they have seized 32 tonnes of packaged marijuana with a street value of at least 64 million euros ($A99 million), which they said was the largest amount ever taken globally.
Police raided a series of farms and production plants across Spain in an operation called Gardens. They arrested nine men and 11 women, who were aged between 20 and 59.
"The Civil Guard has seized the largest cache of packaged marijuana found so far," Spain's Civil Guard said in a statement.
"It was equivalent to approximately 1.1 million plants."
Police said the gang dried the marijuana plants, packaged them and sent them to parts of Spain, Switzerland, Holland, Germany and Belgium.
The gang were detained in Toledo, Ciudad Real, Valencia and Asturias last month but details of the operation were made only public on Saturday.
In June, the Spanish Tax Agency said, in reference to a different drugs operation, that cannabis was worth up to 2500 euros ($A3,859) per kilogram.