diff --git a/CHANGELOG.md b/CHANGELOG.md
index dde87957..9ba743f2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -36,7 +36,8 @@
     - `salmon/salmon_quant`: Transcript quantification from RNA-seq data (PR #24).
 
 * `samtools`: 
-    - `samtools/index`: Index SAM/BAM/CRAM files.
+    - `samtools/flagstat`: Counts the number of alignments in SAM/BAM/CRAM files for each FLAG type (PR #31).
+    - `samtools/index`: Index SAM/BAM/CRAM files (PR #33).
 
 ## MAJOR CHANGES
 
diff --git a/src/samtools/samtools_flagstat/config.vsh.yaml b/src/samtools/samtools_flagstat/config.vsh.yaml
new file mode 100644
index 00000000..20a5e3cd
--- /dev/null
+++ b/src/samtools/samtools_flagstat/config.vsh.yaml
@@ -0,0 +1,51 @@
+name: samtools_flagstat
+namespace: samtools
+description: Counts the number of alignments in SAM/BAM/CRAM files for each FLAG type.
+keywords: [ stats, mapping, counts, bam, sam, cram ]
+links:
+  homepage: https://www.htslib.org/
+  documentation: https://www.htslib.org/doc/samtools-flagstat.html
+  repository: https://github.com/samtools/samtools
+references: 
+  doi: [10.1093/bioinformatics/btp352, 10.1093/gigascience/giab008]
+license: MIT/Expat
+
+argument_groups:
+  - name: Inputs
+    arguments:
+    - name: --bam
+      type: file
+      description: |
+        BAM input files.
+    - name: --bai
+      type: file
+      description: |
+        BAM index file.
+  - name: Outputs 
+    arguments:
+    - name: --output
+      type: file 
+      description: |
+        File containing samtools stats output.
+      direction: output
+      example: output.flagstat
+   
+resources:
+  - type: bash_script
+    path: script.sh
+test_resources:
+  - type: bash_script
+    path: test.sh
+  - type: file
+    path: test_data
+engines:
+  - type: docker
+    image: quay.io/biocontainers/samtools:1.19.2--h50ea8bc_1
+    setup:
+      - type: docker
+        run: |
+          samtools --version 2>&1 | grep -E '^(samtools|Using htslib)' | \
+          sed 's#Using ##;s# \([0-9\.]*\)$#: \1#' > /var/software_versions.txt
+runners:
+- type: executable
+- type: nextflow
\ No newline at end of file
diff --git a/src/samtools/samtools_flagstat/help.txt b/src/samtools/samtools_flagstat/help.txt
new file mode 100644
index 00000000..fe54d20c
--- /dev/null
+++ b/src/samtools/samtools_flagstat/help.txt
@@ -0,0 +1,13 @@
+```sh
+samtools flagstat --help
+```
+Usage: samtools flagstat [options] <in.bam>
+      --input-fmt-option OPT[=VAL]
+               Specify a single input file format option in the form
+               of OPTION or OPTION=VALUE
+  -@, --threads INT
+               Number of additional threads to use [0]
+      --verbosity INT
+               Set level of verbosity
+  -O, --output-fmt FORMAT[,OPT[=VAL]]...
+               Specify output format (json, tsv)
\ No newline at end of file
diff --git a/src/samtools/samtools_flagstat/script.sh b/src/samtools/samtools_flagstat/script.sh
new file mode 100644
index 00000000..beac3703
--- /dev/null
+++ b/src/samtools/samtools_flagstat/script.sh
@@ -0,0 +1,11 @@
+#!/bin/bash
+
+## VIASH START
+## VIASH END
+
+set -e
+
+samtools flagstat \
+    "$par_bam" \
+    > "$par_output"
+    
\ No newline at end of file
diff --git a/src/samtools/samtools_flagstat/test.sh b/src/samtools/samtools_flagstat/test.sh
new file mode 100644
index 00000000..ec5a5b07
--- /dev/null
+++ b/src/samtools/samtools_flagstat/test.sh
@@ -0,0 +1,47 @@
+#!/bin/bash
+
+test_dir="${meta_resources_dir}test_data"
+echo ">>> Testing $meta_functionality_name"
+
+"$meta_executable" \
+  --bam "$test_dir/a.bam" \
+  --bai "$test_dir/a.bam.bai" \
+  --output "$test_dir/a.flagstat"
+
+echo ">>> Checking whether output exists"
+[ ! -f "$test_dir/a.flagstat" ] && echo "File 'a.flagstat' does not exist!" && exit 1
+
+echo ">>> Checking whether output is non-empty"
+[ ! -s "$test_dir/a.flagstat" ] && echo "File 'a.flagstat' is empty!" && exit 1
+
+echo ">>> Checking whether output is correct"
+diff "$test_dir/a.flagstat" "$test_dir/a_ref.flagstat" || \
+    (echo "Output file a.flagstat does not match expected output" && exit 1)
+
+rm "$test_dir/a.flagstat"
+
+############################################################################################
+
+echo ">>> Testing $meta_functionality_name with singletons in the input"
+
+"$meta_executable" \
+  --bam "$test_dir/test.paired_end.sorted.bam" \
+  --bai "$test_dir/test.paired_end.sorted.bam.bai" \
+  --output "$test_dir/test.paired_end.sorted.flagstat"
+
+echo ">>> Checking whether output exists"
+[ ! -f "$test_dir/test.paired_end.sorted.flagstat" ] && echo "File 'test.paired_end.sorted.flagstat' does not exist!" && exit 1
+
+echo ">>> Checking whether output is non-empty"
+[ ! -s "$test_dir/test.paired_end.sorted.flagstat" ] && echo "File 'test.paired_end.sorted.flagstat' is empty!" && exit 1
+
+echo ">>> Checking whether output is correct"
+diff "$test_dir/test.paired_end.sorted.flagstat" "$test_dir/test_ref.paired_end.sorted.flagstat" || \
+    (echo "Output file test.paired_end.sorted.flagstat does not match expected output" && exit 1)
+
+rm "$test_dir/test.paired_end.sorted.flagstat"
+
+
+
+echo "All tests succeeded!"
+exit 0
\ No newline at end of file
diff --git a/src/samtools/samtools_flagstat/test_data/a.bam b/src/samtools/samtools_flagstat/test_data/a.bam
new file mode 100644
index 00000000..dba1268a
Binary files /dev/null and b/src/samtools/samtools_flagstat/test_data/a.bam differ
diff --git a/src/samtools/samtools_flagstat/test_data/a.bam.bai b/src/samtools/samtools_flagstat/test_data/a.bam.bai
new file mode 100644
index 00000000..12f5f510
Binary files /dev/null and b/src/samtools/samtools_flagstat/test_data/a.bam.bai differ
diff --git a/src/samtools/samtools_flagstat/test_data/a_ref.flagstat b/src/samtools/samtools_flagstat/test_data/a_ref.flagstat
new file mode 100644
index 00000000..5d8b9a73
--- /dev/null
+++ b/src/samtools/samtools_flagstat/test_data/a_ref.flagstat
@@ -0,0 +1,16 @@
+6 + 0 in total (QC-passed reads + QC-failed reads)
+6 + 0 primary
+0 + 0 secondary
+0 + 0 supplementary
+0 + 0 duplicates
+0 + 0 primary duplicates
+6 + 0 mapped (100.00% : N/A)
+6 + 0 primary mapped (100.00% : N/A)
+6 + 0 paired in sequencing
+3 + 0 read1
+3 + 0 read2
+6 + 0 properly paired (100.00% : N/A)
+6 + 0 with itself and mate mapped
+0 + 0 singletons (0.00% : N/A)
+0 + 0 with mate mapped to a different chr
+0 + 0 with mate mapped to a different chr (mapQ>=5)
diff --git a/src/samtools/samtools_flagstat/test_data/script.sh b/src/samtools/samtools_flagstat/test_data/script.sh
new file mode 100755
index 00000000..fc32b48e
--- /dev/null
+++ b/src/samtools/samtools_flagstat/test_data/script.sh
@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# Download test data from snakemake wrapper
+
+wget https://raw.githubusercontent.com/snakemake/snakemake-wrappers/3a4f7004281efc176fd9af732ad88d00c47d432d/bio/samtools/flagstat/test/mapped/a.bam
+samtools index a.bam
+# samtools flagstat a.bam > a_ref.flagstat
+
+
+# Download test data from nf-core module
+
+wget https://github.com/nf-core/test-datasets/raw/modules/data/genomics/sarscov2/illumina/bam/test.paired_end.sorted.bam
+wget https://github.com/nf-core/test-datasets/raw/modules/data/genomics/sarscov2/illumina/bam/test.paired_end.sorted.bam.bai
+# samtools flagstat test.paired_end.sorted.bam > test_ref.paired_end.sorted.flagstat
\ No newline at end of file
diff --git a/src/samtools/samtools_flagstat/test_data/test.paired_end.sorted.bam b/src/samtools/samtools_flagstat/test_data/test.paired_end.sorted.bam
new file mode 100644
index 00000000..85cccf14
Binary files /dev/null and b/src/samtools/samtools_flagstat/test_data/test.paired_end.sorted.bam differ
diff --git a/src/samtools/samtools_flagstat/test_data/test.paired_end.sorted.bam.bai b/src/samtools/samtools_flagstat/test_data/test.paired_end.sorted.bam.bai
new file mode 100644
index 00000000..0c6d5a96
Binary files /dev/null and b/src/samtools/samtools_flagstat/test_data/test.paired_end.sorted.bam.bai differ
diff --git a/src/samtools/samtools_flagstat/test_data/test_ref.paired_end.sorted.flagstat b/src/samtools/samtools_flagstat/test_data/test_ref.paired_end.sorted.flagstat
new file mode 100644
index 00000000..4028563d
--- /dev/null
+++ b/src/samtools/samtools_flagstat/test_data/test_ref.paired_end.sorted.flagstat
@@ -0,0 +1,16 @@
+200 + 0 in total (QC-passed reads + QC-failed reads)
+200 + 0 primary
+0 + 0 secondary
+0 + 0 supplementary
+0 + 0 duplicates
+0 + 0 primary duplicates
+197 + 0 mapped (98.50% : N/A)
+197 + 0 primary mapped (98.50% : N/A)
+200 + 0 paired in sequencing
+100 + 0 read1
+100 + 0 read2
+192 + 0 properly paired (96.00% : N/A)
+194 + 0 with itself and mate mapped
+3 + 0 singletons (1.50% : N/A)
+0 + 0 with mate mapped to a different chr
+0 + 0 with mate mapped to a different chr (mapQ>=5)