Kevin Youkilis was born March 15, 1979, in Cincinnati Ohio. “Kevin was the most enthusiastic player that I can ever remember in three decades of coachng,” Ted Schumacher said. “Yet, he was never the heralded ‘star.’ . . . Kevin was a steady performer but far from sensational. Yet his work ethic and passion were second to none. He simply would never quit.”

After he graduated from Sycamore High School in 1997, two Division 1 schools recruited him: Butler University and his ultimate choice, the University of Cincinnati. Youkilis chose Cincinnati over Butler University, because both his father and his long-time idol, Sandy Koufax, had attended UC.

The UC Bearcats had just had a terrible season of 12-46. At a winter camp the Bearcats Manager (Brian Cleary) spotted Youkilis and would later recount his impressions of the young player this way: “I looked at him and said, ‘Well, we need somebody.’ I’d love to tell you I saw something no one else did, but he was just better than what we had.” Indeed he was.  Youkilis excelled  all four years he played at UC and would become one of the few All-Americans to play as a Bearcat. 

Kevin Youkilis was drafted by the Boston Red Sox in the eighth round of the 2001 Major League Baseball amateur draft.  In June, 2001, Youkilis made his pro debut. In that season, Youkilis walked so much that he tied the Minor League record for reaching base in consecutive games–an amazing string of 71. He got on base so much while he was in the Minor Leagues that his team nicknamed him ‘The Greek Of God of Walks.” Kevin reaches base half of the times he’s up to bat. When Youkilis was with the Sea Dogs, he walked 86 times in 94 games. Youkilis has such good vision he can  see the last row of the eye-test chart, in fact he  has 10/20 vision.

A coach at the time summarized Youk’s prospects as follows:  “I think he has a chance to play in the big leagues. The test now is to see him at another level.”  “If he’s able to make the adjustment (to Triple-A), I think he has a good chance. He’s been on the right path. If he keeps progressing up the ladder and is able to handle the pitching at each level you’ll see him (in Boston).”

In college and the minors, Youkilis' on-base ability became the dominant aspect of his game. He had an on-base percentage of .549 during his senior season at Cincinnati, then reached base at an above-.500 rate again in his first professional season with the Lowell Spinners. For the whole of his minor league career, Youkilis posted a .442 on-base percentage. He was Boston's Minor League Player of the Year in both 2001 and 2002 and he earned spots on All-Star teams in AA and AAA.

Kevin Youkilis made his Major League debut in 2004, hitting a home run in his first at-bat with the Red Sox. As a rookie, Youkilis bounced between the ML and AAA levels, hitting .260 with a .367 on-base percentage and seven home runs in 208 at-bats in Boston. He spent his 2005 season in much the same capacity as his road to a permanent spot in the Majors remained blocked by veteran starters.

Come 2006, Kevin Youkilis became a fulltime starter with the Red Sox. In 680 plate appearances, he reached base at a .381 rate, adding 13 home runs, 42 doubles, and 100 runs scored. In the Majors, he has improved his OPS in every season. His 2007 season featured a pickup in power numbers as he hit 16 home runs and slugged .453, serving as a key cog in Boston's World Series Championship.

In the 2008 season, Kevin Youkilis evolved into an MVP candidate. With a .312 average, .390 on-base percentage, 29 home runs, and 115 RBI, Youkilis made the All-Star team and finished third in AL MVP voting. His 2009 season was a continuation of his power surge as he hit .305 with 27 home runs and reached base at a career-high .413 clip. Youkilis once again made the All-Star team and finished sixth in MVP voting.

As strong as his offensive game is, Kevin Youkilis has made a name for himself on the defensive side of the game as well. Though he started his professional career as a third baseman, Youkilis was one of baseball's best defensive first basemen. When the Red Sox acquired third baseman Mike Lowell entering the 2006 season, Youkilis became the team's fulltime first baseman. In 2007, Youkilis took home the American League Gold Glove Award for first base. Between 2006 and 2008, Youkilis set a Major League record by playing 238 consecutive errorless games at first base.

In 2009, Youkilis was 2nd in the AL in OBP (.413) and OPS (.961), 4th in hit by pitch (16), 5th in slugging percentage (.548), and batted .305 overall and .362 with runners in scoring position.  He also led the AL in pitches per plate appearance (4.42), was 6th in batting average on balls in play (.363), and 10th in walk percentage (13.6%).  Of the players with 1,000 plate appearances in the AL over the 2008–09 seasons, none had a higher OPS than Youkilis (.960).  In the field, while Youkilis split his time primarily between first base and third base and therefore did not qualify for the fielding percentage title at either, his .998 fielding percentage in 78 games at first matched that of the league leader Lyle Overbay, and his .974 fielding percentage in 63 games at third base was better than league-leader Melvin Mora's .971  Youkilis finished sixth in balloting for the 2009 AL MVP Award, receiving two second-place votes.[121] He was selected as the Red Sox most valuable player (winner of the 2009 Thomas A. Yawkey Memorial Award) in voting by the Boston Chapter of the Baseball Writers' Association of America.

In 2010, Youkilis was again named to Sporting News' list of the 50 greatest current players in baseball, ranking No. 38 on the list. A panel of 21 MLB executives was polled to arrive at the list.  On August 2, Youkilis' season was cut short by a right thumb abductor muscle tear, which he had played through for two weeks.  The injury limited him to only 102 games for the season, his fewest since his 2005 sophomore year. Slowed by his injury, he had only 362 at-bats, but batted .307/.411/.564 with 19 home runs and 62 RBIs.

During the offseason the Red Sox acquired All-Star first baseman Adrian Gonzalez, and with the imminent departure of Adrián Beltré, Youkilis agreed to the make the switch back to third base for 2011.  The Red Sox suffered a collapse late in the 2011 season, losing their playoff positioning. A source among the Red Sox claimed that Josh Beckett, Jon Lester, and John Lackey spent games they did not pitch in the clubhouse eating fried chicken and drinking beer; some Red Sox teammates speculated that Youkilis was the source of this information, alienating him from his teammates.  On April 15, 2012, Red Sox manager Bobby Valentine publicly questioned Youkilis' motivation and physical ability to succeed. Viewing rookie Will Middlebrooks as the superior third baseman, Valentine began to play Middlebrooks over Youkilis. The Red Sox traded Youkilis to the Chicago White Sox on June 24th.