diff --git a/lib/completion.zsh b/lib/completion.zsh
index 2b62785d5..ebaab0856 100644
--- a/lib/completion.zsh
+++ b/lib/completion.zsh
@@ -32,9 +32,9 @@ zstyle ':completion:*' list-colors ''
 zstyle ':completion:*:*:kill:*:processes' list-colors '=(#b) #([0-9]#) ([0-9a-z-]#)*=01;34=0=01'
 
 if [[ "$OSTYPE" = solaris* ]]; then
-  zstyle ':completion:*:*:*:*:processes' command "ps -u $USER -o pid,user,comm"
+  zstyle ':completion:*:*:*:*:processes' command "ps -u $USERNAME -o pid,user,comm"
 else
-  zstyle ':completion:*:*:*:*:processes' command "ps -u $USER -o pid,user,comm -w -w"
+  zstyle ':completion:*:*:*:*:processes' command "ps -u $USERNAME -o pid,user,comm -w -w"
 fi
 
 # disable named-directories autocompletion
diff --git a/lib/diagnostics.zsh b/lib/diagnostics.zsh
index 001de42b7..650520797 100644
--- a/lib/diagnostics.zsh
+++ b/lib/diagnostics.zsh
@@ -112,7 +112,7 @@ function _omz_diag_dump_one_big_text() {
   command uname -a
   builtin echo OSTYPE=$OSTYPE
   builtin echo ZSH_VERSION=$ZSH_VERSION
-  builtin echo User: $USER
+  builtin echo User: $USERNAME
   builtin echo umask: $(umask)
   builtin echo
   _omz_diag_dump_os_specific_version
diff --git a/plugins/emacs/emacsclient.sh b/plugins/emacs/emacsclient.sh
index 0aa8d6f40..04a2c2afd 100755
--- a/plugins/emacs/emacsclient.sh
+++ b/plugins/emacs/emacsclient.sh
@@ -20,8 +20,8 @@ _emacsfun()
 # tempfile. (first argument will be `--no-wait` passed in by the plugin.zsh)
 if [ "$#" -ge "2" -a "$2" = "-" ]
 then
-    tempfile="$(mktemp --tmpdir emacs-stdin-$USER.XXXXXXX 2>/dev/null \
-                || mktemp -t emacs-stdin-$USER)" # support BSD mktemp
+    tempfile="$(mktemp --tmpdir emacs-stdin-$USERNAME.XXXXXXX 2>/dev/null \
+                || mktemp -t emacs-stdin-$USERNAME)" # support BSD mktemp
     cat - > "$tempfile"
     _emacsfun --no-wait $tempfile
 else
diff --git a/plugins/screen/screen.plugin.zsh b/plugins/screen/screen.plugin.zsh
index 7009e7a91..c1db8ad92 100644
--- a/plugins/screen/screen.plugin.zsh
+++ b/plugins/screen/screen.plugin.zsh
@@ -2,7 +2,7 @@
 # of the tab window should be.
 if [[ "$TERM" == screen* ]]; then
   if [[ $_GET_PATH == '' ]]; then
-    _GET_PATH='echo $PWD | sed "s/^\/Users\//~/;s/^\/home\//~/;s/^~$USER/~/"'
+    _GET_PATH='echo $PWD | sed "s/^\/Users\//~/;s/^\/home\//~/;s/^~$USERNAME/~/"'
   fi
   if [[ $_GET_HOST == '' ]]; then
     _GET_HOST='echo $HOST | sed "s/\..*//"'
@@ -51,4 +51,4 @@ if [[ "$TERM" == screen* ]]; then
     eval "tab_hardstatus=$TAB_HARDSTATUS_PREFIX:$TAB_HARDSTATUS_PROMPT"
     screen_set $tab_title $tab_hardstatus
   }
-fi
\ No newline at end of file
+fi
diff --git a/plugins/ssh-agent/ssh-agent.plugin.zsh b/plugins/ssh-agent/ssh-agent.plugin.zsh
index 430647135..d45406f63 100644
--- a/plugins/ssh-agent/ssh-agent.plugin.zsh
+++ b/plugins/ssh-agent/ssh-agent.plugin.zsh
@@ -61,11 +61,11 @@ zstyle -b :omz:plugins:ssh-agent agent-forwarding _agent_forwarding
 
 if [[ $_agent_forwarding == "yes" && -n "$SSH_AUTH_SOCK" ]]; then
 	# Add a nifty symlink for screen/tmux if agent forwarding
-	[[ -L $SSH_AUTH_SOCK ]] || ln -sf "$SSH_AUTH_SOCK" /tmp/ssh-agent-$USER-screen
+	[[ -L $SSH_AUTH_SOCK ]] || ln -sf "$SSH_AUTH_SOCK" /tmp/ssh-agent-$USERNAME-screen
 elif [[ -f "$_ssh_env_cache" ]]; then
 	# Source SSH settings, if applicable
 	. $_ssh_env_cache > /dev/null
-	if [[ $USER == "root" ]]; then
+	if [[ $USERNAME == "root" ]]; then
 		FILTER="ax"
 	else
 		FILTER="x"
diff --git a/plugins/systemadmin/README.md b/plugins/systemadmin/README.md
index 243db03f2..052fc6edc 100644
--- a/plugins/systemadmin/README.md
+++ b/plugins/systemadmin/README.md
@@ -10,17 +10,17 @@ plugins=(... systemadmin)
 
 ## Aliases
 
-| Alias   | Command                                                                | Description                                                        |
-|---------|------------------------------------------------------------------------|--------------------------------------------------------------------|
-| ping    | `ping -c 5`                                                            | Sends only 5 ICMP Messages                                         |
-| clr     | `clear; echo Currently logged in on $TTY, as $USER in directory $PWD.` | Clears the screen and prints the current user, TTY, and directory  |
-| path    | `print -l $path`                                                       | Displays PATH with each entry on a separate line                   |
-| mkdir   | `mkdir -pv`                                                            | Automatically create parent directories and display verbose output |
-| psmem   | `ps -e -orss=,args= \| sort -b -k1 -nr`                                | Display the processes using the most memory                        |
-| psmem10 | `ps -e -orss=,args= \| sort -b -k1 -nr \| head -10`                    | Display the top 10 processes using the most memory                 |
-| pscpu   | `ps -e -o pcpu,cpu,nice,state,cputime,args \|sort -k1 -nr`             | Display the top processes using the most CPU                       |
-| pscpu10 | `ps -e -o pcpu,cpu,nice,state,cputime,args \|sort -k1 -nr \| head -10` | Display the top 10 processes using the most CPU                    |
-| hist10  | `print -l ${(o)history%% *} \| uniq -c \| sort -nr \| head -n 10`      | Display the top 10 most used commands in the history               |
+| Alias   | Command                                                                    | Description                                                        |
+|---------|----------------------------------------------------------------------------|--------------------------------------------------------------------|
+| ping    | `ping -c 5`                                                                | Sends only 5 ICMP Messages                                         |
+| clr     | `clear; echo Currently logged in on $TTY, as $USERNAME in directory $PWD.` | Clears the screen and prints the current user, TTY, and directory  |
+| path    | `print -l $path`                                                           | Displays PATH with each entry on a separate line                   |
+| mkdir   | `mkdir -pv`                                                                | Automatically create parent directories and display verbose output |
+| psmem   | `ps -e -orss=,args= \| sort -b -k1 -nr`                                    | Display the processes using the most memory                        |
+| psmem10 | `ps -e -orss=,args= \| sort -b -k1 -nr \| head -10`                        | Display the top 10 processes using the most memory                 |
+| pscpu   | `ps -e -o pcpu,cpu,nice,state,cputime,args \|sort -k1 -nr`                 | Display the top processes using the most CPU                       |
+| pscpu10 | `ps -e -o pcpu,cpu,nice,state,cputime,args \|sort -k1 -nr \| head -10`     | Display the top 10 processes using the most CPU                    |
+| hist10  | `print -l ${(o)history%% *} \| uniq -c \| sort -nr \| head -n 10`          | Display the top 10 most used commands in the history               |
 
 ## Functions
 
diff --git a/plugins/systemadmin/systemadmin.plugin.zsh b/plugins/systemadmin/systemadmin.plugin.zsh
index 03064c035..08136abda 100644
--- a/plugins/systemadmin/systemadmin.plugin.zsh
+++ b/plugins/systemadmin/systemadmin.plugin.zsh
@@ -21,7 +21,7 @@ function retlog() {
 }
 
 alias ping='ping -c 5'
-alias clr='clear; echo Currently logged in on $TTY, as $USER in directory $PWD.'
+alias clr='clear; echo Currently logged in on $TTY, as $USERNAME in directory $PWD.'
 alias path='print -l $path'
 alias mkdir='mkdir -pv'
 # get top process eating memory
diff --git a/themes/adben.zsh-theme b/themes/adben.zsh-theme
index b9ac77d00..7321df724 100644
--- a/themes/adben.zsh-theme
+++ b/themes/adben.zsh-theme
@@ -89,8 +89,8 @@ function precmd {
 
 # Context: user@directory or just directory
 prompt_context () {
-    if [[ "$USER" != "$DEFAULT_USER" || -n "$SSH_CLIENT" ]]; then
-        echo -n "${PR_RESET}${PR_RED}$USER@%m${PR_RESET}${PR_BRIGHT_YELLOW}%~%<<${PR_RESET}"
+    if [[ "$USERNAME" != "$DEFAULT_USER" || -n "$SSH_CLIENT" ]]; then
+        echo -n "${PR_RESET}${PR_RED}$USERNAME@%m${PR_RESET}${PR_BRIGHT_YELLOW}%~%<<${PR_RESET}"
     else
         echo -n "${PR_RESET}${PR_BRIGHT_YELLOW}%~%<<${PR_RESET}"
     fi
diff --git a/themes/agnoster.zsh-theme b/themes/agnoster.zsh-theme
index 99707f684..fe7ddbac6 100644
--- a/themes/agnoster.zsh-theme
+++ b/themes/agnoster.zsh-theme
@@ -88,7 +88,7 @@ prompt_end() {
 
 # Context: user@hostname (who am I and where am I)
 prompt_context() {
-  if [[ "$USER" != "$DEFAULT_USER" || -n "$SSH_CLIENT" ]]; then
+  if [[ "$USERNAME" != "$DEFAULT_USER" || -n "$SSH_CLIENT" ]]; then
     prompt_segment black default "%(!.%{%F{yellow}%}.)%n@%m"
   fi
 }
diff --git a/themes/avit.zsh-theme b/themes/avit.zsh-theme
index 921ed99d3..1e20d8f9f 100644
--- a/themes/avit.zsh-theme
+++ b/themes/avit.zsh-theme
@@ -17,7 +17,7 @@ function _user_host() {
   local me
   if [[ -n $SSH_CONNECTION ]]; then
     me="%n@%m"
-  elif [[ $LOGNAME != $USER ]]; then
+  elif [[ $LOGNAME != $USERNAME ]]; then
     me="%n"
   fi
   if [[ -n $me ]]; then
diff --git a/themes/flazz.zsh-theme b/themes/flazz.zsh-theme
index c0a7fb5d0..e21b52ef5 100644
--- a/themes/flazz.zsh-theme
+++ b/themes/flazz.zsh-theme
@@ -1,4 +1,4 @@
-if [ "$USER" = "root" ]
+if [ "$USERNAME" = "root" ]
 then CARETCOLOR="red"
 else CARETCOLOR="blue"
 fi
diff --git a/themes/obraun.zsh-theme b/themes/obraun.zsh-theme
index 7af44056f..cc2769e4b 100644
--- a/themes/obraun.zsh-theme
+++ b/themes/obraun.zsh-theme
@@ -1,4 +1,4 @@
-if [ "$USER" = "root" ]; then CARETCOLOR="red"; else CARETCOLOR="blue"; fi
+if [ "$USERNAME" = "root" ]; then CARETCOLOR="red"; else CARETCOLOR="blue"; fi
 
 local return_code="%(?..%{$fg[red]%}%? ↵%{$reset_color%})"
 
diff --git a/themes/re5et.zsh-theme b/themes/re5et.zsh-theme
index 95af1e2ee..bdf342f49 100644
--- a/themes/re5et.zsh-theme
+++ b/themes/re5et.zsh-theme
@@ -1,4 +1,4 @@
-if [ "$USER" = "root" ]; then CARETCOLOR="red"; else CARETCOLOR="magenta"; fi
+if [ "$USERNAME" = "root" ]; then CARETCOLOR="red"; else CARETCOLOR="magenta"; fi
 
 local return_code="%(?..%{$fg_bold[red]%}:( %?%{$reset_color%})"
 
diff --git a/themes/sunrise.zsh-theme b/themes/sunrise.zsh-theme
index 2111576c3..11f6af127 100644
--- a/themes/sunrise.zsh-theme
+++ b/themes/sunrise.zsh-theme
@@ -9,7 +9,7 @@ Y=$fg_no_bold[yellow]
 B=$fg_no_bold[blue]
 RESET=$reset_color
 
-if [ "$USER" = "root" ]; then
+if [ "$USERNAME" = "root" ]; then
     PROMPTCOLOR="%{$R%}" PROMPTPREFIX="-!-";
 else
     PROMPTCOLOR="" PROMPTPREFIX="---";
diff --git a/tools/install.sh b/tools/install.sh
index d4ecb7afe..cfc2808fe 100755
--- a/tools/install.sh
+++ b/tools/install.sh
@@ -227,7 +227,7 @@ EOF
   if [ -n "$SHELL" ]; then
     echo "$SHELL" > ~/.shell.pre-oh-my-zsh
   else
-    grep "^$USER:" /etc/passwd | awk -F: '{print $7}' > ~/.shell.pre-oh-my-zsh
+    grep "^$USERNAME:" /etc/passwd | awk -F: '{print $7}' > ~/.shell.pre-oh-my-zsh
   fi
 
   # Actually change the default shell to zsh