Auction house Sotheby's has invited sealed bids to be received by June 26 for the nearly 300 year-old instrument made by the Italian master craftsman Antonio Stradivari in 1719.
Musical instrument expert Tim Ingles described the sale of the instrument, one of only 10 Stradivarius violas still in existence, as a "once in a lifetime" event.
Known as the "Macdonald" viola in a reference to a previous owner -- Baron Macdonald who purchased it in around 1820 -- it is said to be in perfect condition and has never been restored.
The current record for the most expensive instrument sale is held by the 1721 "Lady Blunt" Stradivarius violin which was sold for $15.9 million in June 2011 by the Nippon Music Foundation.
Proceeds from the online auction went to help victims of the 2011 Japanese tsunami and earthquake.