James Wigan of London Thoroughbred Services bought the mare although he could not divulge his client's identity. She will be boarded at the Rothschild family's Waddesdon Stud in Buckinghamshire.
Japan's Shadai Farm, London-based agent Jamie McCalmont, and Sheikh Mohammed's bloodstock agent John Ferguson provided Wigan with his opposition.
Spinning Queen's price eclipsed the previous December record of 2.5 million guineas paid by Satish Sanan in 1997 for both Dance Design and Padua's Pride.The opening-day session saw 207 head sell for 19,568,500 guineas (about $39.7 million), to average 94,534 guineas (about $191,715). The median was 45,000 guineas (about $91,260). The gross was up 69.4%, the average 82.5%, and the median 40.1%.
Last year's opening session 223 head sell for 11,552,800 guineas, to average 51,806. The median was 32,000 guineas.
Group II St Simon Stakes heroine Short Skirt (by Diktat) was another to make seven figures when Ferguson fought off Japanese agent Nobutaka Tada at 1.4 million guineas (about $2.85 million). Agents Luke Lillingston and John Warren were others to bid.
The group I Nunthorpe Stakes heroine La Cucaracha (by Piccolo) was sold for 525,000 guineas to agent James Delahooke, acting for TDN publisher Barry Weisbord and Richard Santulli, who trade as Colts Neck Stables.
Three-year-old Park Esteem (by Singspiel), a half-sister to group I Italian Derby winner Central Park (by In The Wings) offered from Jeremy Noseda's stable, was bought for 580,000 guineas by Australian agent Kieran Moore, acting for the Scone-based Cressfield Stud. Charlie Gordon-Watson was underbidder.