Tom Brady and Gisele SELLING Mega-Estate in L.A.!!!!!

This is really shocking ... the incredible European country estate Tom Brady and Gisele Bundchen spent 4 years and $40 million building is on the market ... less than a year after it was completed.

Our real estate sources tell us ... the couple wants out of L.A. permanently and will be living full- time in Boston, where they're building another ridiculously big estate -- a 14,300 square-foot house on 5 acres. The estate is listed for a cool $50 MILLION!!!

As for the L.A. house, Tom and Gisele personally spent a huge amount of time planning the design. It's an amazing property -- a 14,000 square-foot main house, one of the best home gyms in the world, antiques from everywhere around the globe, an amazing infinity pool, waterfall and pond ... all on 4 prime acres in Brentwood.

There was actually a buzz the New England Patriots QB and his supermodel wife would move to L.A. full-time after he retired, but clearly that's not the case.

What we can't figure out -- why not have 2, more modest $20 million mansions in both cities.

BTW ... we called Tom and Gisele's brokers -- Kurt Rappaport and Stephen Shapiro -- but our calls weren't returned.