Noting the use of the word "created" in the question, there can be only one answer. Creation speaks of the point at which anything begins to exist, so the answer is one of faith, not science. As such, God created oxygen.
If you happen to be Hindu, then Brahma, via his creation by Vishnu is likely responsible for oxygen.
The Azrec belied it was the godmother Teteoh innan.
The Maya belied it was Kukulkán and Tepeu.
The Finnish tell that it was Ilmater, daughter of Sky.
The ancestors of the Scandinavians, Anglos, and Saxons believed it was done by the gods Odin, Vili, and Vé.
According to the ancient Hawai'ian Kumulipo (creation story) it just happens in a Big Bang/evolution sort of way, up to the point that the four divine beings (Laʻilaʻi (Female), Kiʻi (Male), Kane (God), and Kanaloa (Octopus)), in the eighth wa.
Different ideas have risen throughout the history of man. No one has the market cornered though and respect for all is important.
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Shortly after the birth of the universe. It is an element.
Oxygen was created by fusion in the cores of stars and distributed through the universe when those stars exploded.
There is no oxygen in space. The oxygen in space stations is created through a process called electrolysis, which uses energy from solar panels to split water (H2O) into hydrogen gas (H2) and oxygen gas (O2).
When one atom of Oxygen forms a convalent bond with two atoms of Hydrogen the compound known as water will be created.
oxygen was created by trees.Trees were created from bacteria and living organisms.Trees create oxygen that we need to survive.
Oxygen Studios was created in 2007.
Oxygen Education was created in 2001.
Oxygen Games was created in 2004.
Oxygen Green Party was created in 1998.
Oxygen Project was created on 2008-01-11.
Oxygen - film - was created on 1999-11-12.
Oxygen of Love was created on 1996-09-06.
Diary of an Oxygen Thief was created in 2006.
Oxygen Design Agency was created in 1996.
Ozone is created by the oxygen molecules. When the UV falls on oxygen, ozone is formed.
Oxygen - Marie Serneholt song - was created in 2006.