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PEOPLE GROUP PROFILE

The Big Sepik of Papua New Guinea

The Big Sepik of Papua New Guinea, numbering approximately 18,500 people, are No Longer Unreached. They are described as an indigenous ethnic group of Papua New Guinea They are an Indigenous people, with Big Sepik as their ethnic/kinship group and are in the New Guinea people cluster of the Pacific Islander Peoples. Their primary religion is Roman Catholicism. They primarily speak Iatmul.

Photo by Google. (2025). Image generated by Gemini 2.5 Flash: Big Sepik

Fast Facts:

Affinity Group: Pacific Islander Peoples
Country: Papua New Guinea
People Cluster: New Guinea
Primary Language(s): Iatmul (ian)
Primary Religion(s): Roman Catholicism
Population: 18,500
Strategic Progress Index (SPI): No Longer Unreached
Global Status of Evangelical Christianity (GSEC): 5% or Greater but Less than 10% Evangelical
People Group ID: PG009782
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Pray for the Big Sepik of Papua New Guinea

Join others around the world in praying for the lost to be saved, the gospel to advance, the global Church to grow, and for laborers to be sent out and sustained in the harvest.

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Dig Deeper (Religion):

Primary Religion: Roman Catholicism
Religious Affiliation: Christianity

73%
%
Roman Catholicism Adherents

Dig Deeper (Language):

Primary Language: Iatmul
Language Family: Ndu

65%
%
Iatmul Speakers

Media Resources in Iatmul:

Films:

No entries found for: Iatmul(ian). Help build some!

Provided by the Jesus Film Project

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Bible Resources in Iatmul:

Provided by Faith Comes by Hearing

Or check out the Iatmul bible at Bible.com

Linked from YouVersion

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Explore Lostness and Next Steps

Unengaged and Unreached

Strategic Priority Index (SPI): Unengaged and Unreached (SPI: 2), which means there are less than 2% evangelical Christian populations among which there are no known efforts focused on establishing self-sustaining churches consistent with evangelical faith and practice.
Lostness Priority Index (LPI): Marginally Reached People Group, (LPI: 4), 3% to 6% Evangelical.
Global Status of Evangelical Christianity (GSEC): 5% or Greater but Less than 10% Evangelical (GSEC: 5), this people group is greater than or equal to 5% evangelical

Next steps for the Big Sepik:
Begin signifcant prayer and fasting for this group
Send cross-cultural teams to discover and research this people group
Begin gospel seed sowing and church planting among this group

SPI: Unreached yet Engaged

The Big Sepik are Engaged yet Unreached, which means there are less than 2% evangelical Christian populations but there are sustained efforts at establishing self-sustaining churches consistent with evangelical faith and practice.

Next steps for the Big Sepik:
Continue prayer and fasting for this group
Continue gospel seed sowing and church planting among this group
Begin training up local leaders to lead and develop strategies to reach their own people

SPI: No longer Unreached

The Big Sepik are No Longer Unreached, which means there are more than 2% evangelical Christian populations and there are churches consistent with evangelical faith and practice. There is still more to be done among them.

Next steps for the Big Sepik:
Empower local believers to begin praying for their own people
Continue gospel seed sowing and church planting
Encourage local leaders to being leading church planting strategy and looking for Unreached and Unengaged groups nearby

Pray specifically for the Big Sepik of Papua New Guinea

For by him all things were created, in heaven and on earth, visible and invisible, whether thrones or dominions or?rulers?or authorities—all things were created through him and for him.
readColossians 1:16

Pray for those who are lost among them, that they will come to know the One who created all things and holds all things together.

All the ends of the earth shall remember and turn to the LORD, and all the families of the nations shall worship before you. For kingship belongs to the LORD, and he rules over the nations.
readPsalm 22:27-28

Pray that entire families will turn to the Lord in repentance and faith, and that they will worship Him and declare His righteousness to the nations.

Now therefore go, and I will be with your mouth and teach you what you shall speak.
readExodus 4:12

Pray that as people place their faith in Christ, God will equip them with the words and wisdom to proclaim His message effectively.

Jesus said to them again, "Peace be with you. As the Father sends me, even so I am sending you."
readJohn 20:21

Ask God to raise up and send out believers cross-culturally who will go out in His authority and be sustained by His peace as they share the gospel with the lost.

Big Sepik Across Countries (ROP3 - 101423) reported in the following countries:

To download a comprehensive people group list in spreadsheet form, visit our Research Data page.

Peoplegroups.org relies on updates from the field and other organizations for much of our data, so if you have any updates, please contact us. We use various international naming standards. For a list of these standards and fields, visit our Definitions page.

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