Have we ever seen a sporting year like 2015? From American Pharoah's run to the Triple Crown to Ronda Rousey's MMA dominance to Jordan Spieth's taking aim at golf's Grand Slam, it's been a remarkable year in athletic achievement, one of the best ever. Below are the 12 leading contenders for 2015 Sportsman of the Year. Sports Illustrated's editors will make its (very tough) selection next month, but we want our readers to have their say. Below, cast your vote for the person (or, in Pharoah’s case, superhorse) you think is the most worthy selection for Sportsman of the Year. Leading up to the announcement on Dec. 14, we'll also be publishing a series of essays from our writers and peers of the 12 contenders that make the argument for each candidate.

2015 Sportsman of the Year contenders

Simone Biles

The 18-year-old gymnast is poised to make a Gabby Douglas-like splash in Rio next Summer, but already has a number of impressive achievements on the mat. In 2015, she secured her third straight all-around title at the U.S. National Championships and led the U.S. team to their third consecutive gold medal at the World Artistic Gymnastics Championships.

Usain Bolt

At the Beijing World Championships, Bolt defended his titles in the 100, 200m and 4x100 events, and also recorded the world’s fastest recorded time in the 200 (19.55 seconds). With the wins at Beijing, he now holds the record for most medals in World Championships history.

Steph Curry

Curry was the leading vote-getter for the 2015 All-Star Game, won the league’s Most Valuable Player award, fueled a 67-win season from the Warriors and capped it off with a Finals victory over LeBron James & Co. He also set a record for most three-pointers (286) made in a season and helped Golden State evolve the game with its small-ball attack.

Thomas Davis

Davis is a fantastic every-down linebacker for the Carolina Panthers but his accomplishments extend far beyond the playing field. He won the 2014 Walter Payton Man of the Year award for his work with the Thomas Davis Defending Dreams Foundation, a non-profit that gives away scholarships and puts on a number of events for underprivileged children in America and their families.

Novak Djokovic

Calling it the best year of his life, 28-year-old Djokovic won 10 titles in 2015, including three Grand Slams and six ATP Masters 1000 series crowns. His match record in 2015 currently sits at 78–5 including an unbeaten run to 22 matches, dating back to August 23 (a loss to Roger Federer in the Cincinnati Masters final).

Carli Lloyd

Lloyd scored three goals within the first 16 minutes of play to lead the United States to a 5–2 victory over Japan in the World Cup final. Her hat trick was the fastest in World Cup history—men or women—and her six goals in the World Cup earned her the Golden Ball award as the tournament’s best player

Lionel Messi

Messi led Barcelona to the Spanish league and Copa del Rey (domestic cup) titles in addition to winning his fourth UEFA Champions League. The favorite to win World Player of the Year honors for a record fifth time, Messi also led Argentina to the final at Copa America.

American Pharoah

The 3-year-old colt ended a 37-year Triple Crown drought with a huge win in the Belmont Stakes—the 12th Triple Crown winner in history. He completed his career with a 6.5 length win in the $5 million Breeders' Cup Classic in his final start before heading off to the breeding shed.

Ronda Rousey

There may not be an athlete alive more dominant at his or her sport than Rousey. The undefeated UFC women’s bantamweight champion had the best year of her career in 2015, taking out previously unbeaten Cat Zingano via armbar in a mere 14 seconds at UFC 184 and following that up with a 34-second KO of Bethe Correia at UFC 190 in Brazil.

Kansas City Royals

Fueled by a heartbreaking loss to the Giants in the 2014 World Series, the Royals played a thrilling brand of aggressive baseball on their way to winning their first World Series since 1985. They came-from-behind against the Astros in the ALDS, knocked off the Blue Jays in six games the ALCS and finally rolled over the Mets, 4 games to 1.

Jordan Spieth

The 22-year-old Spieth had his coming-out party in 2015, becoming the second youngest golfer to win the Masters and youngest to win the U.S. Open. He recently regained the World No. 1 ranking after a top ten finish at the WGC-HSBC Champions event in China.

Serena Williams

She fell two matches short of completing the calendar Grand Slam but Williams's 2015 was nothing short of incredible: At age 33, she won her 19th, 20th and 21st Grand Slam titles at the Australian Open, French Open and Wimbledon, and finished the year with a 53-3 win-loss record and was the year-end No. 1 for the fifth time in her career.

Voting closes at 11:59 p.m. on Dec. 12 and the winner of our reader poll will be revealed on Dec. 13. Sports Illustrated’s Sportsman of the Year will be announced on Dec. 14. It's your chance to let us know who should take home SI's biggest honor for 2015.