Mejiro Dober (Japanese: メジロドーベル, Hepburn: Mejiro Dōberu; foaled May 6, 1994) is a Japanese racehorse and broodmare. Her major victories include the Hanshin Juvenile Fillies in 1996, the Yushun Himba and the Shuka Sho in 1997, and the Queen Elizabeth II Cup in 1998 and 1999. She received the JRA Award for Best Two-Year-Old Filly, JRA Award for Best Three-Year-Old Filly, JRA Award for Best Horse By Home-bred Sire, and JRA Award for Best Older Filly or Mare consecutively in the years she raced. Yutaka Yoshida rode her in all her races, and she compiled a career record of 10 wins in 21 starts. She was the first racehorse in history to receive annual awards for four consecutive years, and her five wins in JRA Grade I races held the record for the most Grade I wins by a filly until 2009 when Vodka broke the record by achieving seven Grade I wins.

Background Mejiro Dober was foaled on May 6, 1994, at Mejiro Farm in Date, Hokkaido. Her sire, Mejiro Ryan, was the winner of the 1991 Takarazuka Kinen, and she was part of his first crop of foals. Her dam, Mejiro Beauty, was highly regarded as a promising prospect, but she retired after only two wins due to injury.

The year before, Mejiro Beauty had given birth to a colt sired by Sunday Silence; however, that colt developed severe jaundice immediately after birth and died from an infection following repeated blood transfusions, due to neonatal isoerythrolysis. As a result, a blood sample from Mejiro Beauty was sent for testing. The results revealed that Mejiro Beauty had a rare blood type that was compatible with only about 22 percent of Japanese stallions at the time. By that point, Mejiro Ryan had already mated Mejiro Beauty, and Mejiro Ryan was a stallion not compatible with Mejiro Beauty's blood type. Due to neonatal isoerythrolysis, drinking the dam's milk before developing immunity by colostrum can cause life-threatening anemia. After Mejiro Dober was born, she was given colostrum from Mejiro Roland, a one-eyed broodmare who gave birth around the same time. Following the perils at birth, she suffered a leg fracture in early 1995. It was a severe condition in which bone fragments were floating within the joint, but surgery was performed and successfully completed with the full cooperation of the veterinary staff at Shadai Stallion Station in Abira, Hokkaido.

Although Mejiro Farm had achieved great racing success in the early 1990's with horses such as Mejiro Ryan, Mejiro McQueen, and Mejiro Palmer, the farm had not been able to produce notable horses following that generation. After deliberation, Mejiro Farm decided to reform their practices including improving pasture management, grazing methods, and training facilities. Mejiro Dober and Mejiro Bright were among the first to be trained under the farm's new reforms. In February of her two-year-old season, Mejiro Dober was transferred to Tenko Farm in Fukushima Prefecture, specifically under Yoshikichi Okubo's stable, who had been in charge for caring for Dober's maternal line for a lengthy amount of time.

Racing career 1996: two-year-old season

Mejiro Dober made her debut on July 13, 1996, in a maiden race held at Niigata Racecourse. The jockey was Yutaka Yoshida, a young rider in his third year with the Okubo stable. Although she was the fourth favorite that day, Mejiro Dober broke away from the pack in the home stretch after running in a good position and claimed her first victory. In the subsequent Niigata Sansai Stakes, she made her first attempt at a graded stakes race but finished fifth after being boxed in during the race. However, she went on to win the Saffron Sho and the Ichō Stakes in succession, earning a reputation as one of the top fillies in the Kanto region even among colts.

In December, Mejiro Dober competed in the Hanshin Juvenile Fillies, the championship race for 3-year-old fillies. On the day of the race, Seeking the Pearl was the overwhelming favorite at 1.5-to-1, while Mejiro Dober was the second favorite at 5.8-to-1. The race unfolded with the field stretched out in a long line, with Seeking the Pearl in third place and Mejiro Dober in fifth. From the third turn to the final turn, Mejiro Dober moved up to the leading group; leaving Seeking the Pearl, who lacked a finishing kick, behind, she pulled away in the home stretch and won by two lengths over the second-place finisher, She's Princess. Her winning time of 1 minute 34.6 seconds set a new race record, beating the previous mark set by the 1994 winner, Yamanin Paradise, by 0.1 seconds. This was the first Grade I victory for both Yoshida and Okubo, and it marked the first victory by a Kanto-based horse in ten years, since Mejiro Ramonu.

With this victory, she concluded her season and was named the year's JRA Award for Best Two-Year-Old Filly in January of the following year. Furthermore, her sire, Mejiro Ryan, ranked second in the 3-year-old debut sire rankings. Amidst the prominent success of offspring by imported sires and foreign-bred horses, he garnered attention as a rising star among domestically bred sires.

1997: three-year-old season

In 1997, Mejiro Dober began her campaign in March with the Tulip Sho, in preparation for the Oka Sho, the first leg of the Triple Tiara. She was the favorite at 1.3-to-1 odds, but during the race, she could not handle the slow pace; defying jockey Yoshida's attempts to rein her in, she ran with her head held high and finished third. In an interview conducted before the race, Okubo remarked, "This mare's bloodline tends to be a bit too spirited—she has a tendency to want to run—so the biggest challenge will be how she responds when the pace slows down." The Oka Sho was held on April 6 and due to rain was run on a heavy track. Kyoei March, who had won four of her five career starts was the 2.6-to-1 favorite, while Mejiro Dober was the 3.4-to-1 second favorite. While Kyoei March took the lead early, Mejiro Dober raced from the back of the pack. Mejiro Dober moved up from the final turn and made a strong push down the home stretch, but Kyoei March, who had pulled away early, finished 4 lengths ahead, leaving Mejiro Dober in second place.

On May 25, in the Yushun Himba, the second leg of the Triple Tiara, Kyoei March and Mejiro Dober were the favorites, with the former at 2.2-to-1 as the top choice and the latter at 2.9-to-1 as the second favorite. Regarding the distance of 2,400 meters—800 meters longer than the Oka Sho—while Mejiro Dober was considered to have no concerns in terms of pedigree, there was the question of whether she could maintain harmony with jockey Yoshida given her temperament. In front of a crowd of 150,000 spectators, Mejiro Dober—who was kept wearing a blindfold until just before the start—appeared extremely calm, unlike during the Oka Sho when she had been somewhat restless. When the race began, Kyoei March surged to the front as if pushed forward, while Mejiro Dober, just as in her previous race, settled into a position at the rear and ran in perfect harmony with Yoshida throughout the race. In the final straight, she burst forward from the center of the track and won by two and a half lengths over the second-place finisher, Nana Yo Wing. Kyoei March lost speed rapidly over the final 300 meters and finished 11th. Mejiro Dober's great-grandmother, Mejiro Bosatsu, had been trained by Okubo's father, Sueyoshi, and had finished second in the 1966 Oaks; for those familiar with that era, this victory served as redemption for that defeat. Okubo said, "Up until the fourth turn, she was in perfect rhythm—I'd give that a 95 out of 100—so I was confident she'd pick up speed in the home stretch. In the Oka Sho, she lost ground by taking the outside route, so even though we lost, I believed we were the stronger horse." Yoshida added, "I was certain we had won by the middle of the home stretch. Since she's the Champion Three-Year-Old, to be honest, I felt a sense of relief. This proved that our loss in the Oka Sho was solely due to the course loss."

After a summer break, the fall target became the Shuka Sho, the final leg of the Fillies' Triple Crown. Leading up to that race, Mejiro Dober, Kyoei March, and Seeking the Pearl—who, though a foreign-bred horse and therefore ineligible for the Oka Sho and Oaks, had won the G1 NHK Mile Cup—were regarded as the "Big Three". For her first race of the fall, Okubo, taking into account the time between that race and the main event, selected the Sankei Sho All Comers, where she would face older colts. While this race typically attracted top contenders looking ahead to the Tenno Sho (Autumn), that year's field was relatively weak, with Abukuma Polo, regarded as the leading contender. Consequently, Mejiro Dober was backed as the favorite at 2.1-to-1 odds. During the race, just as in the Tulip Sho, she struggled to settle with jockey Yoshida; however, when Yoshida refrained from forcing Mejiro Dober back and let her take the lead, he regained his composure and held on to win by leading from start to finish.

On October 19, in the Shuka Sho, Seeking the Pearl was absent due to a tracheal condition, and the race was viewed as a showdown between the two top contenders, Mejiro Dober and Kyoei March, who had each won their respective preliminary races. On race day, Mejiro Dober's odds stood at 1.7, making her the favorite for the first time, ahead of Kyoei March. In the race, Kyoei March ran in second place while Mejiro Dober settled in the middle of the pack; in the final straight, Mejiro Dober caught Kyoei March—who had taken the lead—with 100 meters to go and won by two and a half lengths, thus becoming a Double Tiara winner. Nobumichi Iwasaki, General Affairs Director at Mejiro Farm, who attended the race on behalf of the farm, commented, "I think it was a fantastic Grade I race where the two horses, who had also competed in the spring, clashed head-to-head in a battle of strength." After this race, Kyoei March shifted to a short-distance racing career between 1200 to 1600 metres, making this their final head-to-head matchup.

At the end of the year, in a fan vote to select entrants for the Arima Kinen Grand Prix, she received 132,690 votes, placing third behind Air Groove and Bubble Gum Fellow (who did not run). On race day, despite being a 4-year-old filly, she was the third favorite behind Marvelous Sunday and Air Groove. In the race, she ran from the middle to the back of the pack, moved up to the leading group at the final turn, but failed to gain momentum in the home stretch and finished eighth behind Silk Justice. In that year's annual awards, she won two categories: JRA Award for Best Three-Year-Old Filly and JRA Award for Best Horse By Home-bred Sire. Meanwhile, Air Groove who won the Tenno Sho (Autumn), finished second in the Japan Cup, and placed third in the Arima Kinen was selected as Horse of the Year, marking the first time in 26 years that a filly had received the honor.

1998: four-year-old season In 1998, Mejiro Dober began her spring campaign with the Nikkei Shinshun Hai where she finished in 8th place. In April, she participated in the Sankei Osaka Hai in where she faced Air Groove. On race day, Air Groove was the overwhelming favorite at 1.2-to-1 odds, while Mejiro Dober was the third favorite. The race unfolded at a slow pace which she struggled with, and she also suffered the misfortune of losing her path in the home stretch, but she still finished second, just three-quarters of a length behind Air Groove. However, she finished fifth in both the subsequent Meguro Kinen and Takarazuka Kinen and Mejiro Dober was sent to rest.