Share !Wimbledon, England (SportsNetwork.com) - Serena Williams is truly grand. The top-ranked American star beat Garbine Muguruza 6-4, 6-4 Saturday in the Wimbledon women's final to capture her fourth straight Grand Slam title. Williams matched the "Serena Slam" she achieved in 2002-03 and joined Steffi Graf as the only women in the Open Era to win four consecutive major championships more than once. "I can't believe I'm standing here with another Serena Slam, so it's really cool," Williams said in an on-court interview following the match. She also won all four major titles from the 2002 French Open to the 2003 Australian Open. If Williams successfully defends her title at the U.S. Open, she will complete a calendar-year Grand Slam, something which hasn't been accomplished since Graf did it in 1988. Williams won her 28th consecutive Grand Slam match and improved to 21-4 in major finals. She is one Grand Slam title short of the Open Era record held by Graf. It appeared that Williams, following a wobbly start, would cruise to a sixth title at the All England Club. She won nine of 10 games to take the first set and build a 5-1 lead in the second. Muguruza, however, had some fight left in her. The 21-year-old Spaniard broke Williams' serve twice and saved a championship point. But Muguruza's momentum quickly faded as she was broken at love. Williams had a bewildered look on her face after Muguruza hit a forehand wide on a second championship point and it took a few seconds for her to realize the match was over. "I didn't even know it was over because (Garbine) was fighting so hard in the end," said Williams, who won her 68th career title. "I was like, okay, do I have to serve again?" Williams, at 33 years and 289 days, became the oldest woman to win a major in the Open Era. Williams had three double faults while getting broken in the opening game of the match. She then squandered two break points as Muguruza took a 4-2 lead. But Williams regrouped against Muguruza, who was appearing in her first Grand Slam final. "The Grand Slam final, for me, you know, is a dream come true," Muguruza said in an on-court interview. Muguruza was bidding to become the first Spaniard to win the Wimbledon women's title since Conchita Martinez in 1994.