diff --git a/cmd/start.go b/cmd/start.go
index eac419e79..89b16145b 100644
--- a/cmd/start.go
+++ b/cmd/start.go
@@ -163,6 +163,7 @@ func init() {
 	startCmd.Flags().StringVarP(&startCmdArgs.Arch, "arch", "a", defaultArch, "architecture (aarch64, x86_64)")
 	startCmd.Flags().BoolVarP(&startCmdArgs.Flags.Foreground, "foreground", "f", false, "Keep colima in the foreground")
 	startCmd.Flags().StringVar(&startCmdArgs.Hostname, "hostname", "", "custom hostname for the virtual machine")
+	startCmd.Flags().StringVarP(&startCmdArgs.DiskImage, "disk-image", "i", "", "file path to a custom disk image")
 
 	// host IP addresses
 	startCmd.Flags().BoolVar(&startCmdArgs.Network.HostAddresses, "network-host-addresses", false, "support port forwarding to specific host IP addresses")
diff --git a/config/config.go b/config/config.go
index 9c904b383..27ea4c164 100644
--- a/config/config.go
+++ b/config/config.go
@@ -44,6 +44,7 @@ type Config struct {
 	VMType               string `yaml:"vmType,omitempty"`
 	VZRosetta            bool   `yaml:"rosetta,omitempty"`
 	NestedVirtualization bool   `yaml:"nestedVirtualization,omitempty"`
+	DiskImage            string `yaml:"diskImage,omitempty"`
 
 	// volume mounts
 	Mounts       []Mount `yaml:"mounts,omitempty"`
diff --git a/config/configmanager/configmanager.go b/config/configmanager/configmanager.go
index adc5c41f1..219400f7e 100644
--- a/config/configmanager/configmanager.go
+++ b/config/configmanager/configmanager.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/abiosoft/colima/cli"
 	"github.com/abiosoft/colima/config"
@@ -77,6 +78,12 @@ func ValidateConfig(c config.Config) error {
 		}
 	}
 
+	if c.DiskImage != "" {
+		if strings.HasPrefix(c.DiskImage, "http://") || strings.HasPrefix(c.DiskImage, "https://") {
+			return fmt.Errorf("cannot use diskImage: remote URLs not supported, only local files can be specified")
+		}
+	}
+
 	return nil
 }
 
diff --git a/embedded/defaults/colima.yaml b/embedded/defaults/colima.yaml
index fec149807..aa7dc33d7 100644
--- a/embedded/defaults/colima.yaml
+++ b/embedded/defaults/colima.yaml
@@ -197,6 +197,14 @@ sshPort: 0
 # Default: []
 mounts: []
 
+# Specify a custom disk image for the virtual machine.
+# When not specified, Colima downloads an appropriate disk image from Github at
+# https://github.com/abiosoft/colima-core/releases.
+# The file path to a custom disk image can be specified to override the behaviour.
+#
+# Default: ""
+diskImage: ""
+
 # Environment variables for the virtual machine.
 #
 # EXAMPLE
diff --git a/environment/vm/lima/lima.go b/environment/vm/lima/lima.go
index 645113e5b..abd5488ce 100644
--- a/environment/vm/lima/lima.go
+++ b/environment/vm/lima/lima.go
@@ -16,6 +16,7 @@ import (
 	"github.com/abiosoft/colima/environment/vm/lima/limaconfig"
 	"github.com/abiosoft/colima/environment/vm/lima/limautil"
 	"github.com/abiosoft/colima/util"
+	"github.com/abiosoft/colima/util/downloader"
 	"github.com/abiosoft/colima/util/osutil"
 	"github.com/abiosoft/colima/util/yamlutil"
 	"github.com/sirupsen/logrus"
@@ -274,11 +275,34 @@ func (l limaVM) Arch() environment.Arch {
 func (l *limaVM) downloadDiskImage(ctx context.Context, conf config.Config) error {
 	log := l.Logger(ctx)
 
+	// use a user specified disk image
+	if conf.DiskImage != "" {
+		if _, err := os.Stat(conf.DiskImage); err != nil {
+			return fmt.Errorf("invalid disk image: %w", err)
+		}
+
+		image, err := limautil.Image(l.limaConf.Arch, conf.Runtime)
+		if err != nil {
+			return fmt.Errorf("error getting disk image details: %w", err)
+		}
+
+		sha := downloader.SHA{Size: 512, Digest: image.Digest}
+		if err := sha.ValidateFile(l.host, conf.DiskImage); err != nil {
+			return fmt.Errorf("disk image must be downloaded from '%s', hash failure: %w", image.Location, err)
+		}
+
+		image.Location = conf.DiskImage
+		l.limaConf.Images = []limaconfig.File{image}
+		return nil
+	}
+
+	// use a previously cached image
 	if image, ok := limautil.ImageCached(l.limaConf.Arch, conf.Runtime); ok {
 		l.limaConf.Images = []limaconfig.File{image}
 		return nil
 	}
 
+	// download image
 	log.Infoln("downloading disk image ...")
 	image, err := limautil.DownloadImage(l.limaConf.Arch, conf.Runtime)
 	if err != nil {
diff --git a/environment/vm/lima/limautil/image.go b/environment/vm/lima/limautil/image.go
index a877073f0..62b80582c 100644
--- a/environment/vm/lima/limautil/image.go
+++ b/environment/vm/lima/limautil/image.go
@@ -53,6 +53,11 @@ func findImage(arch environment.Arch, runtime string) (f limaconfig.File, err er
 	return img, nil
 }
 
+// Image returns the details of the disk image to download for the arch and runtime.
+func Image(arch environment.Arch, runtime string) (limaconfig.File, error) {
+	return findImage(arch, runtime)
+}
+
 // DownloadImage downloads the image for arch and runtime.
 func DownloadImage(arch environment.Arch, runtime string) (f limaconfig.File, err error) {
 	img, err := findImage(arch, runtime)
diff --git a/util/downloader/download.go b/util/downloader/download.go
index 59ea6997f..7a8eb9be9 100644
--- a/util/downloader/download.go
+++ b/util/downloader/download.go
@@ -5,7 +5,6 @@ import (
 	"os"
 	"path"
 	"path/filepath"
-	"strconv"
 	"strings"
 
 	"github.com/abiosoft/colima/config"
@@ -19,57 +18,6 @@ type (
 	guestActions = environment.GuestActions
 )
 
-type SHA struct {
-	URL    string // url to download the shasum file (if Digest is empty)
-	Size   int    // one of 256 or 512
-	Digest string // shasum
-}
-
-func (s SHA) validate(host hostActions, url, cacheFilename string) error {
-	if s.URL == "" && s.Digest == "" {
-		return fmt.Errorf("error validating SHA: one of Digest or URL must be set")
-	}
-
-	if s.Digest != "" {
-		s.Digest = strings.TrimPrefix(s.Digest, fmt.Sprintf("sha%d:", s.Size))
-	}
-
-	filename := func() string {
-		if url == "" {
-			return ""
-		}
-		split := strings.Split(url, "/")
-		return split[len(split)-1]
-	}()
-	dir, cacheFilename := filepath.Split(cacheFilename)
-
-	var script string
-
-	if s.Digest == "" {
-		script = strings.NewReplacer(
-			"{dir}", dir,
-			"{url}", s.URL,
-			"{filename}", filename,
-			"{size}", strconv.Itoa(s.Size),
-			"{cache_filename}", cacheFilename,
-		).Replace(
-			`cd {dir} && echo "$(curl -sL {url} | grep '  {filename}$' | awk -F' ' '{print $1}')  {cache_filename}" | shasum -a {size} --check --status`,
-		)
-	} else {
-		script = strings.NewReplacer(
-			"{dir}", dir,
-			"{digest}", s.Digest,
-			"{filename}", filename,
-			"{size}", strconv.Itoa(s.Size),
-			"{cache_filename}", cacheFilename,
-		).Replace(
-			`cd {dir} && echo "{digest}  {cache_filename}" | shasum -a {size} --check --status`,
-		)
-	}
-
-	return host.Run("sh", "-c", script)
-}
-
 // Request is download request
 type Request struct {
 	URL string // request URL
@@ -146,7 +94,7 @@ func (d downloader) downloadFile(r Request) (err error) {
 
 	// validate download if sha is present
 	if r.SHA != nil {
-		if err := r.SHA.validate(d.host, r.URL, cacheDownloadingFilename); err != nil {
+		if err := r.SHA.validateDownload(d.host, r.URL, cacheDownloadingFilename); err != nil {
 
 			// move file to allow subsequent re-download
 			// error discarded, would not be actioned anyways
diff --git a/util/downloader/sha.go b/util/downloader/sha.go
new file mode 100644
index 000000000..c1292f863
--- /dev/null
+++ b/util/downloader/sha.go
@@ -0,0 +1,72 @@
+package downloader
+
+import (
+	"fmt"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// SHA is the shasum of a file.
+type SHA struct {
+	Digest string // shasum
+	URL    string // url to download the shasum file (if Digest is empty)
+	Size   int    // one of 256 or 512
+}
+
+// ValidateFile validates the SHA of the file.
+func (s SHA) ValidateFile(host hostActions, file string) error {
+	dir, filename := filepath.Split(file)
+	digest := strings.TrimPrefix(s.Digest, fmt.Sprintf("sha%d:", s.Size))
+
+	script := strings.NewReplacer(
+		"{dir}", dir,
+		"{digest}", digest,
+		"{size}", strconv.Itoa(s.Size),
+		"{filename}", filename,
+	).Replace(
+		`cd {dir} && echo "{digest}  {filename}" | shasum -a {size} --check --status`,
+	)
+
+	return host.Run("sh", "-c", script)
+}
+
+func (s SHA) validateDownload(host hostActions, url string, filename string) error {
+	if s.URL == "" && s.Digest == "" {
+		return fmt.Errorf("error validating SHA: one of Digest or URL must be set")
+	}
+
+	// fetch digest from URL if empty
+	if s.Digest == "" {
+		// retrieve the filename from the download url.
+		filename := func() string {
+			if url == "" {
+				return ""
+			}
+			split := strings.Split(url, "/")
+			return split[len(split)-1]
+		}()
+
+		digest, err := fetchSHAFromURL(host, s.URL, filename)
+		if err != nil {
+			return err
+		}
+		s.Digest = digest
+	}
+
+	return s.ValidateFile(host, filename)
+}
+
+func fetchSHAFromURL(host hostActions, url, filename string) (string, error) {
+	script := strings.NewReplacer(
+		"{url}", url,
+		"{filename}", filename,
+	).Replace(
+		"curl -sL {url} | grep '  {filename}$' | awk -F' ' '{print $1}'",
+	)
+	sha, err := host.RunOutput("sh", "-c", script)
+	if err != nil {
+		return "", fmt.Errorf("error retrieving sha from url '%s': %w", url, err)
+	}
+	return strings.TrimSpace(sha), nil
+}