Pope Francis has said that missionaries are the "heroes of evangelism".

Speaking at morning Mass in Rome, the Pope praised Christians who had given up everything to share their faith. "I'm thinking of them in their last moment on earth, far from their homeland, their families and their loves ones, who said: 'What I did was worth it!"

Comparing them to the apostle Paul, Francis added: "I think it is only right that we give thanks to the Lord for their testimony. It's right that we rejoice for having these missionaries who are true witnesses... They were martyrs who offered up their lives for the Gospel. These missionaries are our glory! The glory of our Church!"

Here are six Christian missionaries who gave up everything for Christ.

Jim Elliot

Jim Elliot was among a group of US missionaries who felt called to share Christ's teaching with the Waodani tribe in Ecuador in the 1950s. At the time, the Waodani were one of the most violent known people groups on earth, who regularly practised homicide and fiercely defended their territory against those wishing to exploit the rich Amazonian land.

Elliot and his fellow missionaries initiated contact with the tribe after being taught some of their language; first by dropping gifts down from a plane and later establishing a camp not far from the Waodani settlement.

In January 1956, however, the five men were killed by members of the tribe as they approached them in person for the first time with the hopes of sharing the gospel.

The story generated worldwide news coverage, and Elliot's wife, Elisabeth, has since written a bestselling book entitled 'Through the Gates of Splendor' about her husband's journey. Jim's journal, which famously features the quote "He is no fool who gives up what he cannot keep to gain that which he cannot lose", has also been read by thousands of believers around the world.

Amazingly, Elisabeth and the sister of another of the missionaries, Rachel, were introduced to the Waodani just two years after their murder, and were invited to live among the tribe. Many of them came to faith.

William Carey

Trained as a shoemaker, William Carey became known as the 'father of modern missions' for his missionary work in India. The story goes that in 1787, he suggested that all Christians had a duty to share the gospel around the world, after which he was told: "Young man, sit down. When God pleases to convert the heathen, he will do it without your aid and mine."

Undeterred, however, he founded the Baptist Missionary Society five years later in 1792, preaching a message during which he said one of his most famous quotes: "Expect great things from God; attempt great things for God".

The next year, he travelled to India with his family, but his struggles continued. He saw no conversions for seven years, his son Peter died of dysentery and his wife's mental health deteriorated rapidly. "This is indeed the valley of the shadow of death to me," Carey wrote at the time. "But I rejoice that I am here notwithstanding; and God is here."

But in 1800, he baptised his first convert to Christianity, and over more than 20 years went on to translate the Bible into dozens of major Indian languages and dialects. He also founded Serampore College to train local ministers.

George Grenfell

A Cornish missionary and explorer, George Grenfell served as a Baptist missionary in Cameroon in the late 1800s.

He was assigned to Cameroon by Carey's Baptist Missionary Society in 1874, and three years later his wife, Mary, died – just 11 months after they'd married. He later transferred to the Congo, and explored the Congo river with Thomas Comber, finding locations for mission stations. He resigned from BMS when it emerged that his Jamaican housekeeper was pregnant with his child. He married her, and was later re-engaged by the society. He is considered to have laid the foundation for Christian witness in tropical Africa.

Mary Slessor

Born in Aberdeen in 1848, Mary Slessor became missionary to Nigeria under the United Presbyterian Church's Foreign Mission Board. Aged just 28, she sailed to West Africa in August 1876 and was assigned to the Calabar region.

This was where the Efik people lived; a community that believed in traditional West African religions and had particular superstition of twins, who were often killed or abandoned.

Slessor saved hundreds of children during her time in Nigeria; even adopting one young girl as her own daughter. She also travelled to dangerous regions where previous male missionaries had been killed, and was known for her pragmatism and sense of humour. She championed women's rights, and set up a mission hospital for the local people.

Slessor suffered from serious bouts of malaria and other tropical diseases, and was forced on more than one occasion to return to Scotland to recover.

She died in Calabar in 1915, aged 67.

Gladys Aylward

Gladys Aylward was a British evangelical Christian missionary to China in the 20th century. Having been raised in North London in a working class family, she initially worked as a housemaid, but had a long-harboured dream of becoming a missionary, and was convinced of her calling to China.

She was rejected by the China Inland Mission after failing to pass the necessary exams, but agreed to work for a 73-year-old missionary, Jeannie Lawson, who was looking for a young woman to carry on her work in the country. When Lawson died, Aylward ran the mission alone.

She went on to serve in the Chinese government as a 'foot inspector' – visiting women all over the country to make sure they were following the new law against foot-binding – which she saw as part of her missionary work. She also adopted a number of orphans, leading around 100 to safety during the Japanese occupation, and became known as 'Ài Wěi Dé', meaning 'Virtuous One'. She died aged 67 in 1970, and her story was made into a film – 'The Inn of the Sixth Happiness'.

CT Studd

Charles Thomas Studd was a famous English cricketer who went on to be a missionary to China, Africa and India. The youngest of the 'Studd Brothers', who were known for their cricket skills at Eton and Cambridge, Charles played in the first Test match between England vs Australia where the Ashes were named.

He was converted to Christianity along with his brothers while at Eton. Of the moment he met God for the first time, he said: "right then and there joy and peace came into my soul. I knew then what it was to be 'born again,' and the Bible which had been so dry to me before, became everything."

When he decided to give up sport to pursue a career as a missionary, he said: "I know that cricket would not last, and honour would not last, and nothing in this world would last, but it was worthwhile living for the world to come."

In his twenties, he served in the China Inland Mission, where he married missionary Priscilla Livingstone Stewart. They lived in China for 10 years, but moved back to the UK due to ill health, before serving in India at a church in Ootacamund.

Later, Prisilla and the couple's four daughter stayed in England, while Charles worked in Central Africa until his death in 1931.

According to his biography by Norman Grubb, in one of his last letters home, Studd wrote: "As I believe I am now nearing my departure from this world, I have but a few things to rejoice in; they are these:

1. That God called me to China and I went in spite of utmost opposition from all my loved ones.

2. That I joyfully acted as Christ told that rich young man to act.

3. That I deliberately at the call of God, when alone on the Bibby liner in 1910, gave up my life for this work, which was to be henceforth not for the Sudan only, but for the whole unevangelized World.

My only joys therefore are that when God has given me a work to do, I have not refused it."