As a four-year-old, she was named the 2015/6 Australian Horse of the Year and middle distance champion after a seven race campaign that included wins in the W. S. Cox Plate and Doncaster Mile.

[7] She was sired by the Irish-bred Street Cry, who won the Dubai World Cup in 2002[8] before becoming a very successful breeding stallion in North America and Australasia.

She started 9/5 favourite for the Australian Oaks over 2400 metres at Randwick on 11 April but was beaten by the 16/1 outsider Gust of Wind, the last race before her winning streak began.

She trailed the large field as they turned for home but finally found racing room and drew off to win by one and three quarter lengths from the colt Ulmann.

"[18] On her final appearance of the season she started odds-on favourite for the Group 1 Queensland Oaks on 30 May at Doomben Racecourse and won by three and a half lengths from Ungrateful Ellen.

[19] After running in a trial at Warwick Farm, Winx began her four-year-old campaign on 12 September 2015 by starting favourite for the Group 2 Theo Marks Stakes over 1300 metres at Rosehill.

Starting favourite against thirteen opponents, she overcame serious interference on the final turn to win by two and a half lengths from the six-year-old gelding Ecuador.

"[22] On 24 October, Winx started favourite for Australia's most prestigious weight-for-age race, the Cox Plate over 2040 metres at Moonee Valley Racecourse.

On 2 April, the filly started odds-on favourite for the A$3 million Doncaster Mile at Randwick despite carrying top weight in a fifteen-runner field on unsuitably soft ground.

She looked unlikely to obtain a clear run in the straight but broke through in the closing stages to win by two lengths from Happy Clapper.

"[26] The win in the Doncaster earned Winx a rating of 126 by the International Federation of Horseracing Authorities (IFHA), which tied her for the lead in the April 2016 listing of the World's Best Racehorse rankings with California Chrome.

"When you think of the great mares of the last decade, only horses like Black Caviar, Treve, Zenyatta, Rachel Alexandra and Danedream have been able to run to figures of 127 and higher.

[5] Winx made her final start of the autumn on 8 April at Royal Randwick in the Queen Elizabeth Stakes, the world's most valuable 2000 metre turf race with a purse of A$4 million.

[47] Winx earned her second Australian Champion Racehorse of the Year award in a ceremony held on 8 October, becoming only the fourth mare to win this honour twice (Sunline, Makybe Diva and Black Caviar being the others).

Coming from last on the turn and still last at the 300m mark, she lengthened stride and finished fast to run Foxplay down right on the line to win by a half neck in a "remarkable" effort.

Winx seemed slow to respond but then picked up her stride in mid stretch and swept to the lead, then eased off slightly near the wire to win by 1+1⁄4 lengths.

[53] Winx made her first start at Flemington Racecourse on 7 October in the Turnbull Stakes, causing "commuter chaos" as her fans headed to the track.

On 3 March, Winx was entered in the Chipping Norton Stakes at Randwick, facing seven rivals including Victoria Derby winner Prized Icon.

"[61] On 24 March, Winx won the George Ryder Stakes for the third time, extending her winning streak to 24 – just shy of Black Caviar's Australian record of 25.

In what Bowman called a tactical race, Winx settled near the back of the six-horse field then started to make up ground around the turn.

With 800m remaining in the race, Winx moved alongside Happy Clapper at the back of the pack while Japanese runner Ambitious pushed Gailo Chop for the lead.

She set an Australasian record by extending her winning streak to 26, bypassing Black Caviar who won 25 races in an undefeated career.

[78] On 16 February, Winx (10-1 on) won the Group 2 Apollo Stakes for a record third time, beating second favourite Happy Clapper (10-1) by over two lengths and stablemate Egg Tart into third place.

[81] On 23 March, Winx won the George Ryder Stakes over heavy ground in what was expected to be her final start at Rosehill; her home and training track.

"Although it's a beautiful afternoon", noted Bowman, "the ground is significantly testing [classified a "Heavy 8"], and it was quite similar to how it was two years ago when she annihilated Le Romain.

Source: Racenet, Racing.com Profiles[3][17] On 17 May 2017, it was announced that Winx would be inducted into the Australian Racing Hall of Fame, becoming only the third horse after Sunline and Black Caviar to be so honored while still in training.

[86] On 2 December 2018, it was announced that Winx had won the 2018 Secretariat Vox Populi Award, earning top votes from online racing fans in a record 60 countries.

"Winx represents everything Mom envisioned when she created this award and reaffirms her notion that a beloved horse will captivate fans and draw interest to the sport no matter where they race.

On the back of her Apollo and Chipping Norton Stakes wins she rated at 125, equal with Hong Kong-based Beauty Generation and the USA's City of Light.

[90][91] On 24 October 2020, a statue by Louis Laumen showing her winning her fourth Cox Plate was unveiled at Moonee Valley Racecourse.