The Arsenal manager was impressed enough by England in their performances against Germany, a 3-2 win, and Netherlands, a 2-1 loss, to put Roy Hodgson's side among the favourites for the tournament.
Wenger said he missed the loss to Netherlands but watched the win over Germany and liked what he saw from England.
"I was impressed and I made them [among the] favourites straight away," the Frenchman said.
"I had been a bit cautious as I thought the super favourites were Germany, France and Spain with England behind, but now they are up there on the list.
"I didn't see the second game against Holland, I saw the France game [against Russia]."
Wenger ranked his home nation as another contender, particularly on home soil, provided they can sort their internal issues out and achieve squad harmony.
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"They are [also among the] favourites because they have so many good players, but they have as well their internal debate about [whether to play Karim] Benzema or not," he said.
"They create their own problems."
Wenger says Germany remain contenders as well, adding: "Germany suffered a lot against England, and I must say I was impressed by England. They were 2-0 down and Germany scored a goal that was not offside so they had a chance of 3-0.
"I must tell you even at 2-0 down I was impressed by England, but if they had lost 3-0 what would the conclusion have been in the press?"