My encounter took place at a farmhouse in Lamington National Park, Queensland, Australia. The farmhouse is very old and was previously owned by the O'Reilly family. The house is regularly rented out to holidayers and I have stayed there on several occasions.
On my last of these (2-4 years ago) I saw something which I believe was a ghost.

It was late at night, and the layout of the house made it a great place to play hide-and-seek in the dark. I was the seeker and decided to start my search in the main bedroom. There was a fire in the room opposite (the two rooms shared a doorway) so I could vaguely make out the contents of the bedroom. As I entered the room however I was forced to stop as directly in front of me a pitch-black shape had appeared out of thin-air. I can't specifically describe the shape as it had no distinct edge and was hazy and unclear. This could be owed to the fact that the room was very dark. The thing was roughly the size of a person and stood/hovered at my eye-level. It was completely pitch-black, I cannot stress this point enough, it was hard, cold, pure, impenetrable black, despite the light from the fire which meant I should have been lit up at least to some degree.

I could easily make out the contents of the room on either side of it. Almost as soon as it had appeared a dark red point of light, where I imagine it's right eye would have been, appeared and began to grow brighter. At this point I felt no fear, merely surprise and confusion at its sudden appearance. I quickly decided that I no longer wanted to enter the room as the thing clearly didn't want me to. As I stepped backwards, the red eye began to fade again and the entire thing vanished.

After having explored the rest of the house and finding all but one of the hiders, I decided it was time to search the main bedroom again. This time, no strange shape challenged me and I quickly found the last hider on top of the wardrobe. Thinking that what I had seen could possibly have been him, I asked if he had been hiding there the entire game, to which he said he had.

There could have been no way for him to have gotten up or down from that wardrobe without making enough noise for me to hear him from anywhere else in the house.

Others have suggested that what I saw could have been my own shadow. However I have since tested this theory by trying to recreate the atmosphere and have had no success at recreating the thing I saw. Due to the low angle of the fire behind me, my shadow should have been much larger than myself projected at the back of the room. The thing I saw was much closer to my size and was clearly right in front of me.