"I am very sorry. I made a mistake and it won't happen again," the king told Spanish state television TVE as he left a Madrid hospital, where he underwent hip surgery last weekend after falling on the hunting trip in Botswana.
The trip was intended to be a private outing for the 74-year-old king, unknown to the media and most Spaniards, until he was rushed back to Madrid and underwent replacement surgery on his right hip.
In his brief apology, the king did not mention the hunting trip, but state television and other Spanish media reported that he was clearly referring to that.
Spaniards generally hold the king in high regard for his service to the nation and his defense of democracy after the death of the dictator Francisco Franco in 1975 -- especially the king's decisive stand to halt a right-wing military coup in 1981.
But after news emerged of the expensive hunting trip, with widespread Spanish media reports that it included the hunting of elephants, even normally-staunch political allies of the monarch said publicly that they considered the timing of the trip a mistake. Some called on him to apologize.
Earlier Wednesday, speculation was rife in Spanish media that he would do so upon leaving the hospital, where doctors said in a medical report that he is recovering well from the hip surgery.
The king said he will resume his responsibilities. His son, Crown Prince Felipe, has stood in for him at some events this week while he was in the hospital.
The criticism of the trip initially focused on the expensive safari in the midst of the nation's deep crisis, with 23% unemployment, 5 million Spaniards out of work, and the government applying austerity cuts and tax increases to make up for budget shortfalls.
The king himself had previously expressed his concern over the impact of the crisis on Spaniards and called on the nation to come together to get through the tough times.
The royal household has a budget of 8.26 million euros ($10.8 million) this year, 2% less than last year, and had recently announced cuts of about $222,000, including trimming salaries of the highest-paid staffers at the royal palace.
Some critics also wondered how much public money was spent for security on the king's private trip.
The criticism later included animal rights activists, as reports emerged that the king was hunting elephants. At least one photo, said to be from an earlier trip, showed the king, rifle in hand, standing in front of a dead elephant. It was widely published last weekend in Spanish media, which said it was taken from the website of an African safari outfitter, and that the photo was later removed from the company's site.
The criticism of the king comes amid frequent mention of the royal household in the news lately, much of it in an uncustomary unflattering light.
Earlier this month, the king's 13-year-old grandson shot himself in the foot with a shotgun during target practice with his father, who is divorced from the king's eldest daughter, Princess Elena. The legal age in Spain to handle firearms, even when accompanied by an adult, is 14.
And the king's son-in-law, Inaki Urdangarin, who is married to the youngest daughter, Princess Cristina, is a suspect in a financial fraud scandal in which public funds earmarked for his foundation allegedly were diverted for private use. Urdangarin denies the charges.
But last December, the royal household said Urdangarin would not take part in official ceremonies, which is a key role for members of the royal family. Urdangarin and his family were not present at Easter for the royal family's traditional photo.
Also last December, the royal family publicly revealed its finances for the first time in an effort to boost public confidence and transparency.
