Sam Poo (died 19 December 1865) was a Chinese bushranger in Australia who was active in New South Wales during early 1865. Poo emigrated to Australia in the early 1860s during the gold rush. Being an unsuccessful miner, he turned to bushranging. He robbed travellers on the Gulgong–Mudgee for several weeks. On 3 February 1865, Poo killed Senior Constable John Ward, who was looking for him. After the murder of Ward, the New South Wales Police organised a large-scale manhunt, which lasted two weeks and resulted in Poo being arrested and seriously injured during his arrest.

Poo was tried two times after his arrest. The first time on 10 April, he was tried for shooting with intent to kill at Aboriginal tracker Henry Hughes during his arrest and he was found guilty by the jury. The second time on 10 October, he was tried for the wilful murder of John Ward and he was again found guilty by the jury. He was sentenced to death and he was executed by hanging on 19 December 1865. Poo was fictionalised in David Martin's novel The Hero of Too (1965) and since has been a theme of a circus show, a children's novel and a planned feature film.

Sam Poo was not his real name, as a Chinese equivalent for it does not exist. Robert Macklin suggests that it is either a derogatory nickname created by white settlers and used by the police or a slang rendering of similar syllables. Macklin also describes the first theory as the more likely one. Several newspaper articles in 1930s and 1940s have referred to a Chinese man who killed Constable Ward as "Li Hang Chiak", but none of the articles mention Sam Poo as Chiak's alternative name. He was also nicknamed "Cranky Sam" and "Phantom Chinaman".

Sam Poo was a Chinese emigrant to Australia during the Gold Rush. He worked as a "hatter" (miner prospecting without a partner who would warn them of dangers) at Talbragar River between present-day Dunedoo and Mudgee in New South Wales. Being an unsuccessful miner, he turned to bushranging. He began practising pidgin-English, horse riding and shooting, using a tree stump as his target. His Chinese compatriots, who were scrupulously law-abiding, described him as a solitary character and said he was "no good".

He was armed with a shotgun and a pistol, and he would lie at a hideaway on the Gulgong–Mudgee road where he'd wait for pedestrians whom he threatened and demanded all their valuables. His victims were mostly Chinese but he also targeted white settlers. Several days prior to the killing of John Ward, Poo allegedly threatened a Mudgee woman, Elizabeth Golding, after speaking with her daughter. According to Golding, Poo said to her "if I cannot have my will of the girl, I will of you".

On 2 February 1865, Poo robbed a hut of a shepherd who was in the employment of farmer James Plunkett and later that day he threatened to shoot two stockmen if they didn't inform him of the topography of the locality. After these two events, locals sent for the police stationed at Denison Town who arrived at midnight. The next morning, Plunkett, Mr. S. E. Plumb, and the police set out to scour the bush for Poo but they were unsuccessful. When they returned at around midday, they found out that Poo had just visited a shepherd's hut a quarter of a mile from the head station. After receiving directions from the shepherd's wife, they proceeded their search towards Mudgee but they were again unsuccessful. At around 5 pm, they met two travellers who said that a bushranger addressed them in a threatening manner about 4 miles (6.4 kilometres) up the road. Travellers described him as a Chinaman with a revolver in the belt and gun on the shoulder. After riding 9 miles up the road, Plunkett and police officer Constable Todd found policeman John Ward heavily injured.

At 10 am on 3 February 1865, Senior Constable John Ward of the New South Wales Police Force stationed at Coonabarabran was returning home from a prisoner escort to Mudgee. He was informed by two men that an armed Chinese man was robbing travellers at a locality known as Barney's Reef. After a short search, Ward found Poo's camp and approached him. Poo ran off into the bush after Ward approached him and said "What are you doing — put down your gun." Poo replied "you policeman — me fire" and he shot Ward in the chest. Ward fired several shots back but he did not hit Poo. Shortly afterwards, Ward was found by Plunkett and Todd. Plunkett took Ward to Birriwa station where during the night arrived Doctor William King who treated him and had previously ridden 45 miles (72 kilometres) to reach him. Nevertheless, Ward died the next day at around 4:30 pm and was buried on the same day.

After Ward's death, a manhunt which a 1961 Sydney Morning Herald article described as "one of early Australia's biggest manhunts" ensued. On 18 February, Poo was tracked down by Aboriginal tracker Henry Hughes. Poo was at a gully 10 miles (16 kilometres) from Cobbora when he was found by constables M'Mahon and Burns. Poo fired at them and escaped to the scrub, where two policemen lost him. Afterwards, M'Mahon and Burns returned to Hughes and Senior Constable Todd, who had previously split to search for Poo along the river. Hughes soon found Poo and several shots were exchanged: a shotgun shot fired by Todd clipped Poo's head and neck. Burns then rushed to secure him. When Poo raised himself from the ground and tried to fire again, Burns hit him with the butt-end of his rifle, fracturing Poo's skull and smashing the stock to pieces. On the morning of 20 February, Poo arrived to a gaol in Mudgee where he received medical treatment.